Fixes an embarrassing problem in C parsing.
Function parameters were not being placed above initial references on the `ref_stack`, leading to problems identifying overloadable functions.
This commit corrects the problem, along with roughly 100 side-effect error messages.
Also deletes the parse_context header, which was written in 2011 and never used.
Total remaining errors: 503
Exposes additional errors in AST coercion.
A refactor will follow to improve handling of dependent types, which are presently nontrivial to detect (Linear in number of typedefs).
Increases total error count to 508.