If a loaded object defines a symbol <object>_gmk_unload, assume it's
a function and invoke it whenever the loaded object is unloaded.
Original implementation by Dmitry Goncharov <dgoncharov@users.sf.net>

* NEWS: Announce the change.
* doc/make.texi: Describe the behavior.
* src/gnumake.h: Add information to the comments.
* src/makeint.h (unload_all): Declare a new function.
* src/main.c (die): Invoke unload_all().
* src/load.c (unload_func_t): Declare a new type for unload.
(struct load_list): Remember the unload symbol if it exists.
(load_object): Move the parsing of the object name from load_file.
Check for the _gmk_unload symbol and if found, remember it.
(load_file): Allow load_object to do object filename parsing.
(unload_file): Remove the load_list entry when unloading the object.
(unload_all): Unload all the loaded objects.
* tests/scripts/features/loadapi: Test the unload function.

Add an ABI version both to the header file and passed to the setup
function.  Unfortunately this itself is an ABI break and I couldn't
find a good way to avoid it.

* NEWS: Announce the ABI is not a preview and the incompatibility.
* doc/make.texi: Remove the preview warnings for object loading.
Document the new ABI version argument.
* src/gnumake.h (GMK_ABI_VERSION): Set the ABI version to 1.
Add comments documenting the format of the setup function.
* src/load.c (setup_func_t): Rename from load_func_t.
(load_file): Pass the ABI version to the setup function.
* tests/scripts/features/load: Rework the setup function.
* tests/scripts/features/loadapi: Ditto.

Previously "load:" worked but "load :" failed.  Allow the latter as
well.  This doesn't fix all issues; "load foo :" is still treated
as a load operation for "foo" and ":".  Avoids SV 50413 as well.
* tests/scripts/features/load: Write tests.

When the expanded value of the variable in buf occupies more space
than available in variable_buffer, function variable_buffer_output
reallocates variable_buffer: return a pointer into the new memory,
not the old memory.

* src/expand.c (expand_variable_buf): Preserve the offset of buf and
return that offset into the (potentially reallocated) buffer.
* tests/scripts/features/expand: Add tests.

Original test proposed by Dmitry Goncharov <dgoncharov@users.sf.net>

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).

If -j1 is given explicitly on the command line don't warn about it.

* src/main.c (main): Skip the warning if -j1.
* tests/scripts/features/jobserver: Add a test for this behavior.

Change error and fatal messages to start with lowercase and not
end with a period.  Note a few very common messages were left
as-is, just in case some other tools parse them.

Also modify the test known-good-output to satisfy the messages.

* src/main.c (main): Add "sanitize" to .FEATURES if ASAN is enabled.
* src/expand.c (expand_variable_output): Remember "recursive" setting
in case it's changed by the expansion of the variable.
* src/file.c (rehash_file): If we drop a file from the global 'files'
hash, remember it in rehashed_files.  We can't free it because it's
still being referenced (callers will invoke check_renamed()) but
it will be a leak since it's no longer referenced by 'files'.
* src/remake.c (update_file_1): If we drop a dependency, remember it
in dropped_list.  We can't free it because it's still being referenced
by callers but it will be a leak since it's no longer referenced as
a prerequisite.
* tests/scripts/functions/guile: Don't run Guile tests when ASAN is
enabled.
* tests/scripts/functions/wildcard: Enabling ASAN causes glob(3) to
break!  Don't run this test.
* tests/scripts/features/exec: Valgrind's exec() doesn't support
scripts with no shbang.
* tests/scripts/jobserver: Valgrind fails if TMPDIR is set to an
invalid directory: skip those tests.
* tests/scripts/features/output-sync: Ditto.
* tests/scripts/features/temp_stdin: Ditto.