glsl: Track blocks in the symbol table using the glsl_type instead of the gl_uniform_...

glsl: Track blocks in the symbol table using the glsl_type instead of the gl_uniform_block

Eventually the gl_uniform_block information won't be calculated until
linking.  Block names need to be checked for name clashes during
compiling, so we have to track it differently.

v2: Update the commit message.  Suggested by Carl Worth.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>