mesa/main: prefer R8-textures instead of A8 for glBitmap in display lists

This allows drivers to communicate that they prefer R8 textures rather
than A8 for glBitmap usage.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
50 jobs for !2188 with glbitmap-r8 in 114 minutes and 55 seconds (queued for 3 seconds)
detached
Status Job ID Name Coverage
  Containers
passed #716847
debian-10

00:00:18

passed #716848
debian-9

00:00:18

passed #716846
lava-container:arm64

00:23:41

passed #716891
lava-container:armhf

00:01:58

passed #716849
aarch64
test-container:arm64

00:00:20

failed #716845
lava-container:armhf

00:00:18

 
  Build
passed #716851
lava-build:arm64

00:05:08

passed #716850
lava-build:armhf

00:04:42

passed #716854
meson-arm64

00:03:57

passed #716853
meson-armhf

00:02:29

passed #716856
meson-clang

00:09:26

passed #716859
meson-clover

00:07:21

passed #716860
meson-clover-old-llvm

00:06:17

passed #716862
meson-i386

00:04:35

passed #716852
meson-main

00:10:42

passed #716855
meson-swr-glvnd

00:05:31

passed #716861
meson-vulkan

00:03:00

passed #716863
scons

00:09:35

passed #716864
scons-old-llvm

00:08:21

passed #716857
scons-swr

00:05:57

passed #716858
scons-win64

00:05:01

 
  Test
passed #716887
db410c
arm64_a306_gles2 1/4

00:09:04

passed #716960
db410c
arm64_a306_gles2 2/4

00:04:27

passed #716961
db410c
arm64_a306_gles2 3/4

00:03:32

passed #716890
db410c
arm64_a306_gles2 4/4

00:03:57

passed #716876
mesa-cheza
arm64_a630_gles2

00:04:07

passed #716877
mesa-cheza
arm64_a630_gles31 1/4

00:03:45

passed #716878
mesa-cheza
arm64_a630_gles31 2/4

00:05:05

passed #716879
mesa-cheza
arm64_a630_gles31 3/4

00:04:28

passed #716880
mesa-cheza
arm64_a630_gles31 4/4

00:05:07

passed #716881
mesa-cheza
arm64_a630_gles3 1/6

00:03:33

passed #716882
mesa-cheza
arm64_a630_gles3 2/6

00:03:52

passed #716883
mesa-cheza
arm64_a630_gles3 3/6

00:03:07

passed #716884
mesa-cheza
arm64_a630_gles3 4/6

00:04:00

passed #716885
mesa-cheza
arm64_a630_gles3 5/6

00:03:19

passed #716886
mesa-cheza
arm64_a630_gles3 6/6

00:03:26

passed #716865
lava-rk3288-veyron-jaq
panfrost-t760-test:armhf

00:41:48

passed #717636
lava-rk3399-gru-kevin
panfrost-t860-test:arm64

00:48:03

passed #716867
test-llvmpipe-gles2 1/4

00:03:14

passed #716868
test-llvmpipe-gles2 2/4

00:03:31

passed #716869
test-llvmpipe-gles2 3/4

00:03:49

passed #716870
test-llvmpipe-gles2 4/4

00:03:24

passed #716871
test-softpipe-gles2 1/4

00:01:26

passed #716872
test-softpipe-gles2 2/4

00:01:43

passed #716873
test-softpipe-gles2 3/4

00:01:52

passed #716874
test-softpipe-gles2 4/4

00:01:44

passed #716875
test-softpipe-gles3-limited

00:03:19

failed #716888
db410c
arm64_a306_gles2 2/4

00:06:11

failed #716889
db410c
arm64_a306_gles2 3/4

00:05:45

failed #716866
lava-rk3399-gru-kevin
panfrost-t860-test:arm64

01:00:01