NOTES
=====

Regarding parse_result_t:
If a parse fails, the parse_result_t will be NULL.
If a parse is successful but there's nothing there (i.e., if end_p succeeds), then there's a parse_result_t but its ast is NULL.

Regarding input location:
If parse is successful, input is left at beginning of next thing to be read.
If parse fails, location is UNPREDICTABLE.


If CONSISTENCY_CHECK is defined, enable a bunch of additional internal
consistency checks.

TODO: Add consistency check to the bitreader

We should support the use of parse-table-based parse methods; add a
parse_compile method that must be called before the newly-created
parser is used.