This will emit an error for something like:
#define FOO(x,x) ...
Obviously, it's not a legal thing to do, and it's easy to check.
Add a "make check" test for this as well.
This fixes the following Khronos GLES3 CTS tests:
invalid_function_definitions.unique_param_name_vertex
invalid_function_definitions.unique_param_name_fragment
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
