[Q] Implement FcConfig handling (95%)

[Stephen J. Turnbull]

Michael Sperber writes:

 > +XEmacs: signals out-of-memory if FcConfigBuildFonts fails
 > 
 > Why *out of memory*?

Because that's the way it is documented that FcConfigBuildFonts can
fail.  I figure it's better to suggest the documented reason, instead
of doing

(define-error 'yo-keith
  "Something went wrong in Xft.  Don't ask me, but maybe Keith P knows."
  'wtf-error)

and using that.

My bet is that, this being X, all undocumented errors will crash all
the way back to the BIOS.  WDYT?  :-)