tests: fix for newer Sun Studio C++.

Reported by Dagobert Michelsen at
<http://lists.gnu.org/archive/html/bug-bison/2010-03/msg00023.html>.
* THANKS (Dagobert Michelsen): Add.
* configure.ac (AC_PREREQ): Set to 2.64 so we get the latest
Autoconf macro for handling the restrict keyword.
* gnulib: Update to latest, which no longer overrides that macro
from Autoconf.
(cherry picked from commit 4333ba11c65f428040d54820b6d4c6aa663944d2)

Conflicts:

	configure.ac