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 -dur binutils-2.17.old/bfd/opncls.c binutils-2.17/bfd/opncls.c

--- binutils-2.17.old/bfd/opncls.c	2006-03-16 13:20:16.000000000 +0100

+++ binutils-2.17/bfd/opncls.c	2007-05-01 18:26:11.000000000 +0200

@@ -158,6 +158,13 @@

 {

   bfd *nbfd;

   const bfd_target *target_vec;

+  struct stat s;

+

+  if (stat (filename, &s) == 0)

+    if (S_ISDIR(s.st_mode)) {

+      bfd_set_error (bfd_error_file_not_recognized);

+      return NULL;

+    }

   nbfd = _bfd_new_bfd ();

   if (nbfd == NULL)