xorg: bump libXt to 1.0.6

Bump libXt to 1.0.6 and remove the
xlib_libXt-1.0.5-makestrs-nocc.patch, which has been included in a
better form in upstream:
 http://cgit.freedesktop.org/xorg/lib/libXt/commit/?id=36e9f0d351afbf7fd2595990b2d39e7c551f6420



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>