portability: use -DGNULIB_POSIXCHECK.

Reported by Eric Blake.  See discussions at
<http://lists.gnu.org/archive/html/bug-bison/2009-09/msg00008.html>
and
<http://lists.gnu.org/archive/html/bug-gnulib/2009-10/msg00108.html>.
* HACKING (Release checks): Suggest -DGNULIB_POSIXCHECK.
* bootstrap.conf (gnulib_modules): Add all the printf modules
suggested by -DGNULIB_POSIXCHECK.  Add realloc-posix as
suggested by -DGNULIB_POSIXCHECK for gnulib's own vasnprintf.c.
(excluded_files): Remove m4/printf-posix.m4.
* tests/atlocal.in (LIBS): As for LDADD in src/local.mk, add
lib/libbison.a so gnulib libraries can be linked.

lib/.gitignore

@@ -4,8 +4,10 @@
 /.deps
 /Makefile
 /Makefile.in
+/alloca.in.h
 /argmatch.c
 /argmatch.h
+/asnprintf.c
 /basename-lgpl.c
 /basename.c
 /bitrotate.h
@@ -23,14 +25,23 @@
 /dirname.c
 /dirname.h
 /dup-safer.c
+/dup2.c
 /errno.in.h
 /error.c
 /error.h
 /exitfail.c
 /exitfail.h
 /fd-safer.c
+/float+.h
+/float.in.h
 /fopen-safer.c
 /fopen.c
+/fprintf.c
+/fpucw.h
+/frexp.c
+/frexpl.c
+/fseterr.c
+/fseterr.h
 /getopt.c
 /getopt.h
 /getopt.in.h
@@ -46,9 +57,17 @@
 /inttypes.h
 /inttypes.in.h
 /inttypes_.h
+/isnan.c
+/isnand-nolibm.h
+/isnand.c
+/isnanf-nolibm.h
+/isnanf.c
+/isnanl-nolibm.h
+/isnanl.c
 /localcharset.c
 /localcharset.h
 /malloc.c
+/math.in.h
 /mbrtowc.c
 /mbsinit.c
 /mbswidth.c
@@ -58,14 +77,30 @@
 /obstack.c
 /obstack.h
 /pipe-safer.c
+/printf-args.c
+/printf-args.h
+/printf-frexp.c
+/printf-frexp.h
+/printf-frexpl.c
+/printf-frexpl.h
+/printf-parse.c
+/printf-parse.h
+/printf.c
 /quote.c
 /quote.h
 /quotearg.c
 /quotearg.h
+/realloc.c
 /ref-add.sed
 /ref-add.sin
 /ref-del.sed
 /ref-del.sin
+/signbitd.c
+/signbitf.c
+/signbitl.c
+/size_max.h
+/snprintf.c
+/sprintf.c
 /stamp-h1
 /stdbool.h
 /stdbool.in.h
@@ -75,6 +110,7 @@
 /stdint.in.h
 /stdint_.h
 /stdio--.h
+/stdio-impl.h
 /stdio-safer.h
 /stdio-write.c
 /stdio.in.h
@@ -104,7 +140,12 @@
 /uniwidth.h
 /unlocked-io.h
 /unsetenv.c
+/vasnprintf.c
+/vasnprintf.h
 /verify.h
+/vfprintf.c
+/vsnprintf.c
+/vsprintf.c
 /wchar.h
 /wchar.in.h
 /wchar_.h
@@ -116,5 +157,6 @@
 /xalloc-die.c
 /xalloc.h
 /xmalloc.c
+/xsize.h
 /xstrndup.c
 /xstrndup.h