This currently involves an ugly hack so that every link doesn't result
in all the built-in functions showing up as multiply defined. As soon
as the built-in functions are stored in a separate compilation unit,
ir_function_signature::is_built_in can be removed.
_mesa_glsl_parse_state should be the parent for all temporary allocation
done while compiling a shader. glsl_shader should only be used as the
parent for the shader's final IR---the _result_ of compilation.
Since many IR instructions may be added or discarded during optimization
passes, IR should not ever be allocated to glsl_shader directly.
Done via sed -i s/talloc_parent(state)/state/g and s/talloc_parent(st)/st/g.
This also removes a ton of talloc_parent calls, which may help performance.
