Changed token_number to enum

Also added a comment explaining why token_number can be negative,
and also cleared error in match_error because it was retaining token buffer data.
Moved code around, preliminary steps

This is a code restructuring to give an init -> setup, calculate, teardown structure to the program. Also removes an unnecessary forward declaration.
Adding beginning of token linked list
Started token linked list

The plan here is to get the tokens out of the scanner in the form of a linked list, copied over from our match code to token stuff. once we do that, we can actually start the parser ...
Completed Linked List implementation for tokens