[Fontconfig] Type1 weights and style strings

[Doug Larrick]

A while back you were looking for additional weights that Fontconfig is 
not recognizing when parsing type1 style names.  Here are two:

Demi (as in Demibold)
Book (like Regular)

These names show up frequently in ITC typefaces.

In general, there is very little standardization of weight names.  For 
example, I have a few Adobe fonts in Regular and Medium weights, both 
of which are assigned weight 100. I think it would be useful to be able 
to edit the weight value assigned to a font by fc-cache, perhaps as 
part of fonts.conf (which currently is not even read by fc-cache 
afaict).

-Doug