Wildcard Font Spec Bug

[Andrew Choi]

I have fixed a small bug in fontset.c (fontset_pattern_regexp) by
allocating three additional bytes for holding the '^', '$', and '\0'
characters in the generated regex.

This bug caused problems when handling font specs with proportionally
many wildcard characters.  It caused Emacs to crash (at least on the
Mac) when asked to evaluate (x-list-fonts "*"), for example.  If you
are encountering similar problems, please see if the fix helps.

Also we should consider fixing a similar problem that exists currently
in w32fns.c (w32_font_match).

Andrew.