mesa: Drop the blacklisting of new GL enums.

mesa: Drop the blacklisting of new GL enums.

Now when people need new extensions, they can skip the entire
enum-definition process, and we can stop reviewing new extension XML for
its enum content.

This also brings in a new enum that I wanted to use in enum_strings.cpp
for testing the code generator.

v2: Drop comment about disabled GL_1PASS_EXT test.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>