Aaron Plattner authored Mar 28, 2017 and Emma Anholt committed Mar 28, 2017

Some drivers don't support SHM pixmaps, but rendercheck doesn't care
and tries to use them anyway. This causes the test to abort:

 Beginning SHM blend test from a8
 X Error of failed request:  BadImplementation (server does not implement operation)
   Major opcode of failed request:  130 (MIT-SHM)
   Minor opcode of failed request:  5 (X_ShmCreatePixmap)
   Serial number of failed request:  805
   Current serial number in output stream:  811
 X Error of failed request:  BadDrawable (invalid Pixmap or Window parameter)
   Major opcode of failed request:  139 (RENDER)
   Minor opcode of failed request:  4 (RenderCreatePicture)
   Resource id in failed request:  0x3200215
   Serial number of failed request:  806
   Current serial number in output stream:  811

Fix this by skipping the shmblend tests if the extension is missing or
doesn't support pixmaps.

Signed-off-by: Aaron Plattner <aplattner@nvidia.com>
Reviewed-by: Eric Anholt <eric@anholt.net>