Reviewed by: Keith Packard <keithp@keithp.com>

Reviewed by: Keith Packard <keithp@keithp.com>
memoize strings and share a single copy for all uses. Note that this could
    be improved further by using statically allocated blocks and gluing
    multiple strings together, but I'm basically lazy. In my environment
    with 800 font files, I get a savings of about 90KB.