When two identifiers follow eachother it could be two instruction
mnemonics or one instruction mnemonic and one operand. To fix this
TOKEN_NEWLINE has been reintroduced as a semantic token. The grammar has
been changed to allow empty statements and every instruction and
directive has to end in a newline. Labels do not have to end in a
newline.
In addition to updating the grammar, the implementation of tokenlist,
ast and parser has been updated to reflect these changes.
The linked list is doubly linked so the parser can look forward into it
and error reporting can look backward.
This commmit also reworks main to use the tokenlist instead of dealing
with the lexer manually.
