Comment 184 for bug 1220426

Layman terms (on trusty):

Download patch from the bugzilla and place it in a file, let's say "foo.diff"

$ apt-get build-dep xorg-server
$ apt-get source xorg-server
$ cd xorg-server-1.15.1
$ patch -p1 < ../foo.diff
$ fakeroot debian/rules binary

This should eventually build a couple of .deb packages with the patch incorporated. It is running for me just now. So no news if it worked or not.

Also, it might make sense to modify debian/changelog and add your own version to make it possible to see the change by judging the version number. (e.g. debchange -i, edit and save)