* modules/regex (Files): Add lib/regex_internal.c,

* modules/regex (Files): Add lib/regex_internal.c,
lib/regex_internal.h, lib/regexec.c, lib/regcomp.c, m4/codeset.m4.
(Depends-on): Add extensions.
(Makefile.am): Remove lib_SOURCES; now done by m4 code.
* config/srclist.txt: Add regcomp.c, regex.c, regex.h, regex_internal.c,
regexec.c.
Add regex_internal.h too, but as a comment, since the libc version
is currently broken in gnulib mode.
* lib/regex.c, lib/regex.h: Sync from libc.
* lib/regcomp.c, lib/regexec_internal.c, lib/regex_internal.h, lib/regexec.c:
New files, synced from libc, except that regex_internal.h
currently has a small porting fix.
* m4/regex.m4: Adjust to new libc regex implementation.
(gl_INCLUDED_REGEX): Add AC_LIBSOURCES for
all the .c and .h parts of (the new) regex.
Quote the m4 stuff better.
Check for RE_ICASE bug of old gnulib.
Check for REG_STARTEND of recent libc.
Rename local variables from jm_* to gl_*.
Quote operand of "test -f".
Say "recent enough" version of libc, not "version 2".
(gl_PREREQ_REGEX): Remove AC_FUNC_ALLOCA, since alloca is a
prerequisite module.  Remove AC_HEADER_STDC; no longer needed.
Check for locale.h, isblank, mbrtowc, wcrtomb, wcscoll.
Remove check for btowc, isascii.
Require AM_LANGINFO_CODESET.