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

--- glibc-2.6/sysdeps/unix/sysv/linux/kernel-features.h	2006-07-29 07:43:27.000000000 +0300

+++ glibc-2.6/sysdeps/unix/sysv/linux/kernel-features.h.new	2008-07-26 08:45:06.000000000 +0300

@@ -445,7 +445,7 @@

 /* The *at syscalls were introduced just after 2.6.16-rc1.  Due to the way the

    kernel versions are advertised we can only rely on 2.6.17 to have

    the code.  */

-#if __LINUX_KERNEL_VERSION >= 0x020611

+#if __LINUX_KERNEL_VERSION >= 0x020611 && !defined __alpha__

 # define __ASSUME_ATFCTS	1

 #endif