Newer gcc doesn't like when you switch on an enum and use a value
that isn't declared:

fcname.c: In function 'FcObjectValidType':
fcname.c:299:2: warning: case value '4294967295'
	not in enumerated type 'FcType' [-Wswitch]

So tweak the logic to avoid this warning.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>