Like the DSNLEXER header, this has visibility in over 700
files, whereas well under half actually use any of it
(quite a bit, but not all, of it actually via DSNLEXER)
Many places already forward-declare the OUTPUTFORMATTER type,
by doing that for the others, it still possible to use the
non-IO methods without having to see richio.h.
Don't parse PEGTL twice, once for modelType and once for
model itself.
Also don't do O(n^2) searches on parameter names when
reading libraries.
And, because it's still too slow, multi-thread it.
Saves about 30% of the time to open the sim model
dialog. Pretty much all the remaining time is in PEGTL,
and that's even with short-circuiting it for most param
values.
