Add mainpage of documentation
Do not use meta2asm/overload.h

Overloading a function in C (even only by the number of its arguments)
is a nice idea, but nobody expects this behaviour in C. On top of that
the amount of code that is necessary to implement the feature does not
pay for the few instances where it is used.
Add documentation for meta2asm/status.h
meta2asm: Tokenizer recognizes labels
Add macro ASSERT_STRING_EQUAL to test framework
meta2asm: Tokenizer reports errors
meta2asm: Refactor tokenizer

Use functions from ctype.h to make code more readable.