ok = pfontdesc:BetterMatch(old_match, new_match)
new_match are a closer match
for the font description than those of old_match are, or if old_match is Nil,
determines if new_match is a match at all.
Approximate matching is done for weight and style; other style attributes
must match exactly. Style attributes are all attributes other than family
and size-related attributes. Approximate matching for style considers
#PANGO_STYLE_OBLIQUE and #PANGO_STYLE_ITALIC as matches, but not as good
a match as when the styles are equal.
Note that old_match must match the font description.
NilTrue if new_match is a better match