mesa/glsl: Separate parsing logic from _mesa_get_uniform_location.

mesa/glsl: Separate parsing logic from _mesa_get_uniform_location.

The parsing logic is moved to a new function in the GLSL module,
parse_program_resource_name().  This name was chosen because it should
eventually be useful for handling everything that OpenGL 4.3 calls
"program resources" (e.g. uniforms, vertex inputs, fragment outputs,
and transform feedback varyings).

Future patches will make use of this function for linking transform
feedback varyings.

NOTE: This is a candidate for the 9.1 branch.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>