present: Check that flip and screen pixmap pitches match

If they don't, flipping will result in corrupted display.

Test case:

* Run Xorg at 1920x1080 with no window manager
* glxgears -geometry 2048x1080

The Present extension code in xserver 1.21 will check for this.

Tested-by: Jax Lin <jax.lin@amd.com>
11 jobs for present_check_flip-pitch in 2 minutes and 13 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #146078
xserver-1.13

00:00:23

passed #146079
xserver-1.14

00:00:24

passed #146080
xserver-1.15

00:00:38

passed #146081
xserver-1.16

00:00:24

passed #146082
xserver-1.17

00:00:24

passed #146083
xserver-1.18

00:00:24

passed #146084
xserver-1.18-clang

00:00:47

passed #146085
xserver-1.19

00:00:24

passed #146086
xserver-1.19-clang

00:00:26

passed #146076
xserver-1.20

00:00:32

passed #146077
xserver-1.20-clang

00:00:27