configure.ac: respect 'g' variants of libtool/libtoolize

BSD OS'es (OS X for me) provide GNU tools with prefixed 'g'. To find correct
versions of libtool/libtoolize on those systems search also for
glibtool/glibtoolize.

Signed-off-by: Andreas Bießmann <andreas@biessmann.de>
Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
[yann.morin.1998@free.fr: search for the g-variant first]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <2f1530b54afcb6a00e1d.1395158786@andreas-mbp.er.biessmann.org>
Patchwork-Id: 331467

diff -ru gdb-6.8.orig/bfd/sysdep.h gdb-6.8/bfd/sysdep.h

--- gdb-6.8.orig/bfd/sysdep.h	2007-07-03 16:26:42.000000000 +0200

+++ gdb-6.8/bfd/sysdep.h	2011-08-21 13:33:47.000000000 +0200

@@ -131,7 +131,7 @@

 extern PTR realloc ();

 #endif

-#if !HAVE_DECL_STPCPY

+#if !HAVE_DECL_STPCPY && !defined(stpcpy)

 extern char *stpcpy (char *__dest, const char *__src);

 #endif