x-font-family-list gives incomplete results

[Dave Love]

`x-font-family-list' misses a lot, specifically fonts which are
suitable for offering the user as the default.  E.g. on a Debian
stable system I have this:

(x-font-family-list)
  => (("clean" . t) ("clearlyu") ("clearlyu alternate glyphs") ("clearlyu 
arabic extra") ("clearlyu ligature") ("clearlyu pua") ("fangsong ti" . t) 
("fixed" . t) ("gothic" . t) ("mincho" . t) ("newspaper") ("nil" . t) ("open 
look cursor") ("open look glyph") ("song ti" . t) ("unifont" . t))

(face-font 'default)
  => "-B&H-LucidaTypewriter-Medium-R-Normal-Sans-12-120-75-75-M-70-ISO8859-1"

Note that the lucidatypewriter I'm actually using isn't listed and I
have 64 families according to xfontsel.

The code implementing this looks superficially correct to me.  Am I
missing something?