Fixed various compiler warnings.
Added peek_n method to Tokenizer.
Added note to Tokenizer.
Improved tokenizer ergonomics.
Vastly improved the ergonomics of Tokenizer.
src/tokenizer.rs -> src/token.rs
Use token::___ instead of ___ in parser.rs
Overhauled the tokenizer 'expect' code.
Defined several more token creator functions.
Implemented argument list parsing.
Converted moves to borrows in Parser
Made parser read more than one statement.
Fixed compiler crash in Parser.parse_preprocessor_function_parameters.

I thought I could use Vec.map_in_place() but Expr and Identifier are different sizes (obviously) and it crashed.
Added expect code to Token, added comma.
Completed argument list parser.
More progress.
Fixed a very infuriating bug.
Fixed a method in Parser.
Made Tokenizer iterate over Result<Token,String>
Added new line checking after #define.