Function _glcpp_parser_expand_function

This is a helper function that's essentially part of the * implementation of _glcpp_parser_expand_node. It shouldn't be called * except for by that function. * * Returns NULL if node is a simple token with no expansion, (that is, * although 'node' corresponds to an identifier defined as a * function-like macro, it is not followed with a parenthesized * argument list). * * Compute the comp