Add FC_COLOR

Only adds "color" to pattern if FreeType version supports color.

Based on patch from Jungshik Shin.
Treat color fonts as scalable

All color fonts are designed to be scaled, even if they only have
bitmap strikes.  Client is responsible to scale the bitmaps.  This
is in constrast to non-color strikes...

Clients can still use FC_OUTLINE to distinguish bitmap vs outline
fonts.  Previously FC_OUTLINE and FC_SCALABLE always had the same
value.  Now FC_SCALABLE is set to (FC_OUTLINE || FC_COLOR).

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=87122