glsl: handle 8 and 16 bit ints in glsl_base_type_is_integer

Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
10 jobs for !921 with glsl_types in 8 minutes and 40 seconds (queued for 2 seconds)
detached
Status Name Job ID Coverage
  Containers Build
passed debian #309664

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  Build+Test
passed meson-clang #309666

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passed meson-clover #309670

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passed meson-main #309669

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passed meson-swr-glvnd #309665

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passed meson-vulkan #309671

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passed scons-llvm #309673

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passed scons-nollvm #309672

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passed scons-swr #309667

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passed scons-win64 #309668

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