This specification is also supported on gles2, so let's add support
for gles31 to the test also.

Sadly, because gles2 doesn't support glGetCompressedTexImage, we can't
easily support the test-cases that re-uploads compressed data. Disabling
them and keeping the others are better than nothing, so let's do that
for now.

Similarly, because glGetTexLevelParameteriv isn't supported on gles
before version 3.1, let's set that as the minimum version.

A potential future improvement could be to embed a pre-compressed image
so these tests can run in all cases. But that requires a lot more work,
so I'll leave that for later.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>