Consolidate token type functions
Add operator info functions
Partially implement the algorithm
Implement the algorithm
Split algorithm into token handling functions
Improve dynamic_cat() error handling
Fix get_token() memory leak at eof
Fix memory leaks and similar problems
Fix mistake in algorithm with popping parentheses

- When popping until left parenthesis
    the parenthesis itself should not be popped.
- The right parenthesis handler has to pop
    the left parenthesis itself now.
Improve error handling