[Fontconfig] Excluding fonts

[Keith Packard]

I'm thinking it would be nice to allow people to elide some fonts from 
their configurations.  It seems like there are a couple of ways:

	1)	exclude by path name -- have a regex that matches
		filenames and includes/excludes them.

	2)	exclude by pattern -- have some match rules that
		select fonts by pattern and include/exclude them.

1) would allow us to easily eliminate all .pcf.gz fonts from the 
configuration while 2) would allow us to build "suitcases" if combined 
with some conditional expressions based on X resources or environment 
variables.

Comments?

-keith