xlib_libXt: bump version to 1.1.3

Needed by the bump of xapp_clipboard, itself needed to avoid the
following build failure:

  http://autobuild.buildroot.org/results/1a4f84ad76ad8c4e70bff6878fc232edf46ff8f1/build-end.log



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>