new parser: error recovery needs work

[DJ Delorie]

I would add that, if we're thinking about a message catalog, we
consider assigning both a specific code and a "category" code to each
message.  I.e., for message WPARAMFOO (function parameter warning) it
might also be in category WcDECL (all declaration warnings) and WcANSI
(all ansi-specific warnings).  Not that I'm suggesting a naming
convention, just thinking that grouping the warnings might prove
useful enough to think about it up front.