ly:font-config-add-directory and ly:font-config-add-font

[Gerard McConnell]

Hello, 
Yesterday James Lowe mentioned drew attention to Issue 1204 at:

http://code.google.com/p/lilypond/issues/detail?id=1204

Yet again, an excellent idea from LilyPond's developers.
Could someone please give a brief example of how to use 
   ly:font-config-add-directory 
and 
   ly:font-config-add-font


Thanks,
Gerard