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.
- Exposes all errors in the header file so any user of the api can test
for the specific error conditions
- Mark all static error pointers as const
- Move generic errors into error.h
- Name all errors err_modulename_* for errors that belong to a specific
module and err_* for generic errors.
