little feature wish

[Jay Sachs <jay@eziba.com>]

I'm using stable version (2.16.2). I'd find it really useful to debug
a grammar if the LexerException could include the state it was in
at the point it encountered a problem. Not only that, but have
the generated Lexer.State class have a toString() method which inludes
the text-version (i.e. human-readable without looking at the source)
of the state name.  Has anyone done this already? Would anyone be
interested? The changes seem like they'd be localized to lexer.txt, and
wouldn't be too hard.

jay