As of d98bc0b6 there are two files that are automatically generated:
ui/shader/texture-blit-frag.h and /ui/shader/texture-blit-vert.h. None
of them is wanted to be tracked by git. Put them into the ignore file
then.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>