WIP mesa: Allow for more than one aux buffer again

555f0a88 said "I don't know of any OpenGL drivers since the IRIX days
that support aux color buffers." This turns out not to be the case, the
NVIDIA driver supports 4. It's not a widely used feature as far as we're
aware, but since these are basically just funny names for framebuffer
objects they're now pretty trivial to support.

WIP status:
- Does not in fact allocate any aux buffers yet
- Probably doesn't handle drawable resize correctly
- Not sure if this needs to do anything special to reject aux buffers in
  core contexts or GLES, though invalidate_framebuffer_storage() looks like
  it might handle it right already
- Only exercised at all with llvmpipe so far
- Need to bump __DRI_NUM_BUFFERS
- Not sure if we need to do anything special to hide this from, like, r100

And of course there's no piglit tests, but auxbuffer.c in mesa/demos is
glxgears that draws to AUX0 and then CopyPixels to BACK, so start there.
77 jobs for !1649 with aux-buffer-support
latest detached
Status Job ID Name Coverage
  Container+Docs
manual #4484045
aarch64 manual
arm_build
manual #4484047
manual
arm_test-base
manual #4484040
manual
x86_build-base
manual #4484043
manual
x86_build_old
manual #4484041
manual
x86_test-base
 
  Container 2
created #4484068
arm64_test
created #4484058
i386_build
created #4484049
kernel+rootfs_amd64
created #4484051
aarch64
kernel+rootfs_arm64
created #4484054
aarch64
kernel+rootfs_armhf
created #4484060
ppc64el_build
created #4484062
s390x_build
created #4484056
x86_build
created #4484064
x86_test-gl
created #4484066
x86_test-vk
 
  Meson X86 64
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meson-android
created #4484078
meson-clang
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meson-classic
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meson-clover
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meson-clover-old-llvm
created #4484071
meson-gallium
created #4484073
meson-release
created #4484069
meson-testing
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meson-vulkan
 
  Scons
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allowed to fail
scons-win64
 
  Meson Misc
created #4484089
aarch64
meson-arm64
created #4484091
aarch64
meson-arm64-build-test
created #4484087
aarch64
meson-armhf
created #4484093
meson-i386
created #4484098
meson-mingw32-x86_64
created #4484096
kvm
meson-ppc64el
created #4484094
kvm
meson-s390x
 
  Llvmpipe
created #4484105
llvmpipe-gles2
created #4484106
llvmpipe-traces
created #4484101
piglit-glslparser
created #4484100
piglit-quick_gl
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piglit-quick_shader
 
  Softpipe
created #4484115
softpipe-gl
created #4484108
softpipe-gles2
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softpipe-gles3
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softpipe-gles31 1/2
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softpipe-gles31 2/2
 
  Freedreno
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google-freedreno-db410c
arm64_a306_gles2
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google-freedreno-db410c
arm64_a306_gles3
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google-freedreno-db410c
arm64_a306_gles3_options
created #4484146
google-freedreno-db820c
arm64_a530_gles2
created #4484148
google-freedreno-db820c
arm64_a530_gles3
created #4484150
google-freedreno-db820c
arm64_a530_gles31
created #4484125
google-freedreno-cheza
arm64_a630_bypass
created #4484132
google-freedreno-cheza
arm64_a630_gl
created #4484116
google-freedreno-cheza
arm64_a630_gles2
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google-freedreno-cheza
arm64_a630_gles3
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google-freedreno-cheza
arm64_a630_gles31
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google-freedreno-cheza
arm64_a630_gmem
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google-freedreno-cheza
arm64_a630_noubo
created #4484127
google-freedreno-cheza
arm64_a630_traces
created #4484134
google-freedreno-cheza
arm64_a630_vk
created #4484137
google-freedreno-cheza
arm64_a630_vk_sysmem
 
  Panfrost
created #4484152
mesa-ci-aarch64-lava-collabora
panfrost-t720-gles2:arm64
created #4484153
mesa-ci-aarch64-lava-collabora
panfrost-t760-gles2:armhf
created #4484154
mesa-ci-aarch64-lava-collabora
panfrost-t860-gles2:arm64
created #4484155
mesa-ci-aarch64-lava-collabora
panfrost-t860-gles3:arm64 1/2
created #4484156
mesa-ci-aarch64-lava-collabora
panfrost-t860-gles3:arm64 2/2
created #4484157
mesa-ci-aarch64-lava-collabora
panfrost-t860-traces:arm64
 
  Radv
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radv-fossils
 
  Virgl
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virgl-gl30-on-gl
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virgl-gl31-on-gl
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virgl-gl32-on-gl
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virgl-gles2-on-gl
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virgl-gles31-on-gl 1/2
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virgl-gles31-on-gl 2/2
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virgl-gles3-on-gl
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virgl-traces
 
  Radeonsi
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mesa-ci-aarch64-lava-collabora
radeonsi-stoney-gles2:amd64
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mesa-ci-aarch64-lava-collabora
radeonsi-stoney-gles31:amd64
created #4484168
mesa-ci-aarch64-lava-collabora
radeonsi-stoney-gles3:amd64
created #4484170
mesa-ci-aarch64-lava-collabora
radeonsi-stoney-traces:amd64