named warnings & individual warning control

[DJ Delorie]

>     status_warning (status, "%s does not support the %<%%%c%> %s format",
>                     WARNTYPE_unsupported_std,

Yeah, that was basically the compromise Mark and I talked about.

I slightly favor putting the new WARNTYPE_* option before the string,
rather than between the string and its parameters, just to keep the
string and its parameters together.

I also slightly favor avoiding the word "type" in something with such
an ingrained idea of what a "type" is.  WARNGROUP might be less
confusing.

Alternately, a string representation of the option could be passed,
but that would slow the lookup down.