Synchronise libtool.m4 with version in gcc repository

[Nick Clifton]

Hi Guys,

   I have imported the version of libtool.m4 that is currently at the 
HEAD of the gcc repository into the sourceware repository.  There was 
one new patch, to add AIX 6 support.

Cheers
   Nick

./ChangeLog
2008-02-14  Nick Clifton  <nickc@redhat.com>

	Import this patch from gcc:
	2008-01-24  David Edelsohn  <edelsohn@gnu.org>

	* libtool.m4: Backport AIX 6 support from ToT Libtool.