Relax detection of non-premultiplied alpha cursor data

The stricter detection broke the cursor in some games. Apparently those
use cursor data with premultiplied alpha, but with some pixels having
r/g/b values larger than the alpha value (which corresponds to original
r/g/b values > 1.0), triggering the workaround.

Relax the detection to match what's in the X server since 1.18.4, but
keep the workaround for older versions.

Bugzilla: https://bugs.freedesktop.org/108650
Acked-by: Alex Deucher <alexander.deucher@amd.com>
11 jobs for relax-non-premul-alpha-cursor-detection in 3 minutes and 27 seconds (queued for 2 minutes and 41 seconds)
Status Name Job ID Coverage
  Build
passed xserver-1.13 #44516

00:00:32

passed xserver-1.14 #44517

00:00:37

passed xserver-1.15 #44518

00:00:34

passed xserver-1.16 #44519

00:00:30

passed xserver-1.17 #44520

00:00:30

passed xserver-1.18 #44521

00:00:29

passed xserver-1.18-clang #44522

00:00:33

passed xserver-1.19 #44523

00:00:30

passed xserver-1.19-clang #44524

00:00:33

passed xserver-1.20 #44514

00:00:39

passed xserver-1.20-clang #44515

00:00:37