Currently, the standalone compiler tries to do function inlining before
linking shaders (including linking against the built-in functions).
This resulted in the built-in function _prototypes_ being inlined rather
than the actual function definition.
This is only known to fix a bug in the standalone compiler; most
programs should be unaffected. Still, it seems like a good idea.
NOTE: This is a candidate for the 7.9 branch.
Kenneth Graunke