Replace TYPE_FLAG_PROTOTYPED with two flags

[Michael Elizabeth Chastain]

Wow, Daniel!

My observation with stabs+ matches yours: gcc does not emit a prototype,
but it does correctly mark the formal argument with 'float' or
'double'.

This ought to get a lot more cases correct, with provisions for
more kludges^H^H^H^H^H^H^H extensions if strange compilers show up.

I do think it's a bit of hack for the stabs reader to claim that all
functions are prototyped.  I think TYPE_FLAG_PROTO_KNOWN would be
more accurate.  But it's not like new broken compilers are showing up
all the time (I hope).

Someday, it will all be dwarf-2.

Michael C