heimdal_build: only enable libintl functions if everything was found

heimdal_build: only enable libintl functions if everything was found

do not rely on intl.h being available but also on the functions being usable
This should fix the build on HP-UX

Bug: https://bugzilla.samba.org/show_bug.cgi?id=9911
Signed-off-by: Christian Ambach <ambi@samba.org>
Change-Id: I5dd88d2d5216b778624778455cca99b32d0be58f
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Thu Feb 20 01:28:24 CET 2014 on sn-devel-104