Disable builtin variables and rules immediately, when -R or -r is
added to MAKEFLAGS inside the makefile.

* src/main.c (disable_builtins): Add new function disable_builtins().
(main): Call disable_builtins().
(reset_makeflags): Call disable_builtins().
* tests/scripts/options/dash-r: Add tests.
* tests/scripts/variables/MAKEFLAGS: Update tests.

Avoid cross-contamination between test files by creating a new
working directory for each file, and setting it as the current
directory before starting the tests in that file.

Rename the test output as tNNN.{base,log,diff,mk} where NNN is
a test number starting with 001 for the first test.  It is
slightly more annoying to find diff files since you can't use
autocomplete directly but it is simpler to match things.

Detect the source directory as the location of the test_driver.pl
script, so remove the separate -srcdir option.

* Makefile.am: Remove hacks to create symlinks when building
out-of-tree, and remove -srcdir option from run_make_tests.
* tests/test_driver.pl: Locate $srcpath based on __FILE__, then
compute $toppath as its parent.  Set $scriptpath under $srcpath
and $workpath under the current directory.  Toss $*_filename
and modify get_logfile() etc. to use the suffix directly.  Add
a chdir() around the invocation of the test.
* tests/run_make_tests.pl: Throw out the -srcdir option and use
$srcpath set in test_driver.pl.  The #WORK# helper is no longer
useful so remove it.  Set #PWD# to the current working dir. Always
search the local directory and $srcpath for config-flags.pm.
Use $srcpath for finding the thelp.pl script.
* tests/scripts/features/vpath: Don't put things in work/ as it
is no longer a subdirectory.
* tests/scripts/features/vpathgpath: Ditto.
* tests/scripts/features/vpathplus: Ditto.
* tests/scripts/misc/general1: Ditto.
* tests/scripts/misc/general2: Ditto.
* tests/scripts/options/dash-k: Ditto.
* tests/scripts/options/symlinks: Use $testpath as the working
directory.
* tests/scripts/variables/GNUMAKEFLAGS: Use the test helper to
display env var values (grepping for GNUMAKEFLAGS finds extra things
now that it is our current working directory).

Create a new special variable, .WARNINGS, to allow per-makefile
control over warnings.  The command line settings will override
this.

Move the handling of warning flags to a new file: src/warning.c.
Allow the decode to work with generic strings, and call it from
decode_switches().

* Makefile.am: Add new file src/warning.c.
* build_w32.bat: Ditto.
* builddos.bat: Ditto.
* po/POTFILES.in: Ditto.
* src/makeint.h: #define for the .WARNINGS variable name.
* src/warning.h: Add declarations for methods moved from main.c.
Rename the enum warning_state to warning_action.
* src/warning.c: New file.  Move all warning encode/decode here
from main.c.
* src/main.c: Move methods into warning.c and call those methods
instead.
(main): Set .WARNINGS as a special variable.
* src/job.c (construct_command_argv): Rename to warning_action.
* src/read.c (tilde_expand): Ditto.
* src/variable.c (set_special_var): Update warnings when the
.WARNINGS special variable is set.
* tests/scripts/options/warn: Check invalid warning options.
* tests/scripts/variables/WARNINGS: Add tests for the .WARNINGS
special variable.

Replace the singleton --warn-undefined-variables with infrastructure
to manage multiple warnings: the --warn option can take an action
"ignore", "warn", or "error" (which will apply to all warnings), or
a specific warning type and an action for that type.  Multiple
options can be provided and are consolidated.

* NEWS: Announce the new option.
* doc/make.1: Document in the man page.
* doc/make.texi (Warnings): Document in the user's manual.
* Makefile.am: Add new header warning.h.
* src/warning.h: Define enum for actions and warning types, and
macros to test whether they are set.  Keep the default settings
separate so that we can correctly reconstruct MAKEFLAGS.
* src/makeint.h: Remove deprecated warn_undefined_variables_flag.
* src/main.c: Create global variables to hold warning settings.
(switches): Add a new switch for --warn.
(initialize_warnings): Set the default warning actions.
(main): Call initialize_warnings().
(encode_warning_state, decode_warning_state): Convert warning states
between strings and enums.
(encode_warning_name, decode_warning_name): Convert warning names
between strings and enums.
(decode_warn_flags): Convert a --warn option into enum values.  If
deprecated warn_undefined_variables_flag is set convert it to --warn.
(decode_switches): Don't remove duplicates of --warn since order
matters.  Call decode_warn_flags() to handle --warn.
(define_makeflags): Special-case handling of --warn options written
to MAKEFLAGS: write out the current settings.
* src/read.c (tilde_expand): Use new warning control macros.
* src/variable.c (warn_undefined): Ditto.
* src/job.c (construct_command_argv): Ditto.
* tests/scripts/options/warn: Rename from warn-undefined-variables
and add tests for --warn.
* tests/scripts/variables/MAKEFLAGS: Expect the new behavior.

Previously we used the fact that this line ending expanded to "$ "
which would then expand to the empty string.  This has problems if
you enable warnings for undefined variables, so directly implement
this special (but documented) trick in the GNU Make parser.

As a side-effect this also removes all previous whitespace when
in GNU Make mode (not in POSIX mode) just as it would without "$".

* src/misc.c (collapse_continuations): Check for "$\" and remove it.
* tests/scripts/variables/flavors: Add regression tests including
with previous whitespace, and escaped/unescaped "$"

Original patches provided by Igor Todorovski <itodorov@ca.ibm.com>
Reworked by Paul Smith <psmith@gnu.org>.
Thanks to IBM for providing a test system.

* NEWS: Announce support.
* AUTHORS: Ditto.
* README.zOS: Provide details on building GNU Make on z/OS.
* build.sh (get_mk_var): z/OS sh has a strange bug which causes it to
generate extra lines of output: rework the function to print output
as we compute it instead of collecting it into a variable, which
works around this bug.
* src/makeint.h: Declare MK_OS_ZOS if we're building for z/OS.
* src/arscan.c: Don't include <ar.h> on z/OS.
* src/job.c: We can't change environ in ASCII mode on z/OS.
* src/main.c: Ditto.  Also we can't use pselect() on z/OS.
* src/posixos.c: pselect() seems to hang on z/OS: don't use it.
* tests/run_make_tests.pl: Handle different exit codes on z/OS.
* tests/test_driver.pl: Preserve some special z/OS env.vars.
Add special checks to output comparisons when on z/OS.
* tests/scripts/features/archives: Don't validate names.  Don't
try to compile empty files as IBM compilers complain.
* tests/scripts/features/shell_assignment: Fix octal value of #.
* tests/scripts/features/temp_stdin: Don't print "term".
* tests/scripts/functions/shell: Handle shell exit codes.
* tests/scripts/targets/ONESHELL: Ditto.
* tests/scripts/targets/POSIX: sh -x prints differently.
* tests/scripts/variables/SHELL: Ditto.

If a parent target has an exported variable that is private, don't
export it in child targets.

* NEWS: Mention this change.
* src/variable.c (target_environment): Ignore private inherited
variables.
* tests/thelp.pl: Add a new "env" operation to show env.var. values.
* tests/scripts/variables/private: Verify this new behavior.

* maintMakefile: Apply spelling fixes.
* src/file.c: Ditto.
* src/misc.c: Ditto.
* src/remake.c: Ditto.
* src/vmsjobs.c: Ditto.
* src/w32/pathstuff.c: Ditto.
* tests/test_driver.pl: Ditto.
* tests/run_make_tests.com: Ditto
* tests/scripts/features/implicit_search: Ditto
* tests/scripts/features/output-sync: Ditto
* tests/scripts/features/patternrules: Ditto
* tests/scripts/features/se_explicit: Ditto
* tests/scripts/features/statipattrules: Ditto
* tests/scripts/functions/foreach: Ditto
* tests/scripts/variables/MAKEFLAGS: Ditto