* ftfont.c: Distingish more carefully between FcChar8 and char.

* ftfont.c: Distingish more carefully between FcChar8 and char.

The previous code passed unsigned char * to a functions like
strlen and xstrcasecmp that expect char *, which does not
conform to the C standard.
(get_adstyle_property, ftfont_pattern_entity): Use FcChar8 for
arguments to FcPatternGetString, and explicitly cast FcChar8 * to
char * when the C standard requires it.