[cache] Signature fixes. * src/cache/ftcglyph.c, src/cache/ftcglyph.h (FTC_GNode_Compare): Remove redundant function. It is equivalent to `ftc_gnode_compare` and becomes completely meaningless with fixed signatures. Update all callers. * src/cache/ftcsbits.c, src/cache/ftcsbits.h (FTC_SNode_Compare): Remove redundant function. It is equivalent to `ftc_snode_compare` and becomes completely meaningless with fixed signatures. Update all callers.