Module Martel.Parser
Implement Martel parsers.
The classes in this module are used by other Martel modules and not
typically by external users.
There are two major parsers, 'Parser' and 'RecordParser.' The first is
the standard one, which parses the file as one string in memory then
generates the SAX events. The other reads a record at a time using a
RecordReader and generates events after each read. The generated event
callbacks are identical.
At some level, both parsers use "_do_callback" to convert
mxTextTools tags into SAX events.
XXX finish this documentation
XXX need a better way to get closer to the likely error position when
parsing.
XXX need to implement Locator