[PATCH 3/3] Fix unresolved symbols

[Guido Günther <agx sigxcpu org>]

Hi,
when using --no-undefined we need to explicitly link against X11 for
XkbGetKeyboard and friends. Attached patch does this if the X11
development files are available. This should be o.k. since platforms
using X11 for GDK have it installed since it's listed as a pkg-config
dependency.
It should also fix building with binutils-gold.
Cheers,
 -- Guido