Integrate changes #8608,8609,8610,8611,8612,8613 from maintperl.

perl's internal variables are not for public consumption,
move their docs from perlapi.pod to perlintern.pod

support for -Dusethreads build under HP-UX 10.20 and DCE threads
library (11.0 and later have pthreads but 10.x don't)

avoid uninitialized value warnings

canonicalize paths when doing chdir() on windows (or Cwd::getcwd()
gets weird results)

perldoc nit on windows

make it possible to run the tests outside the source tree
(there's still a dependency on ../lib being the library
location)

p4raw-link: @8612 on //depot/maint-5.6/perl: 21b80573951053245624647c6ea0077acae22b99
p4raw-link: @8611 on //depot/maint-5.6/perl: 706e8e4d2d0a6985197cb1cb76dc3d2575cd159e
p4raw-link: @8610 on //depot/maint-5.6/perl: fc1aae957f18d75529c72450055ab0d424b7d318
p4raw-link: @8609 on //depot/maint-5.6/perl: 13b98125bf15a4dfacaa2c6f56d3742c97180500
p4raw-link: @8608 on //depot/maint-5.6/perl: f893c726cdaa1ccdec167db9b2ff5c2fdc19e29b

p4raw-id: //depot/perl@8614
p4raw-integrated: from //depot/maint-5.6/perl@8596 'copy in'
	t/lib/dprof/V.pm t/op/flip.t utils/perldoc.PL (@8159..)
	win32/bin/search.pl (@8166..) t/io/tell.t (@8175..)
	hints/hpux.sh (@8601..) thread.h (@8606..) 'ignore'
	pod/perlintern.pod (@7766..) pod/perlapi.pod (@8605..) 'merge
	in' intrpvar.h t/base/term.t (@7895..) win32/vdir.h (@8156..)
	thrdvar.h (@8602..) perlapi.c (@8606..)

1 files changed, 72 insertions, 0 deletions

diff --git a/pod/perlintern.pod b/pod/perlintern.pod
index 6af18b507c..8bfe5a3cd3 100644
--- a/pod/perlintern.pod
+++ b/pod/perlintern.pod
@@ -46,6 +46,78 @@ True if this op will be the return value of an lvalue subroutine
 =for hackers
 Found in file pp.h
 
+=item PL_DBsingle
+
+When Perl is run in debugging mode, with the B<-d> switch, this SV is a
+boolean which indicates whether subs are being single-stepped.
+Single-stepping is automatically turned on after every step.  This is the C
+variable which corresponds to Perl's $DB::single variable.  See
+C<PL_DBsub>.
+
+	SV *	PL_DBsingle
+
+=for hackers
+Found in file intrpvar.h
+
+=item PL_DBsub
+
+When Perl is run in debugging mode, with the B<-d> switch, this GV contains
+the SV which holds the name of the sub being debugged.  This is the C
+variable which corresponds to Perl's $DB::sub variable.  See
+C<PL_DBsingle>.
+
+	GV *	PL_DBsub
+
+=for hackers
+Found in file intrpvar.h
+
+=item PL_DBtrace
+
+Trace variable used when Perl is run in debugging mode, with the B<-d>
+switch.  This is the C variable which corresponds to Perl's $DB::trace
+variable.  See C<PL_DBsingle>.
+
+	SV *	PL_DBtrace
+
+=for hackers
+Found in file intrpvar.h
+
+=item PL_dowarn
+
+The C variable which corresponds to Perl's $^W warning variable.
+
+	bool	PL_dowarn
+
+=for hackers
+Found in file intrpvar.h
+
+=item PL_last_in_gv
+
+The GV which was last used for a filehandle input operation. (C<< <FH> >>)
+
+	GV*	PL_last_in_gv
+
+=for hackers
+Found in file thrdvar.h
+
+=item PL_ofs_sv
+
+The output field separator - C<$,> in Perl space.
+
+	SV*	PL_ofs_sv
+
+=for hackers
+Found in file thrdvar.h
+
+=item PL_rs
+
+The input record separator - C<$/> in Perl space.
+
+	SV*	PL_rs
+
+=for hackers
+Found in file thrdvar.h
+
 =item start_glob
 
 Function called by C<do_readline> to spawn a glob (or do the glob inside