[cache] Fit FTC_GNode_Compare() to FTC_Node_CompareFunc.

* src/cache/ftcglyph.h (FTC_GNode_Compare): Add the 3rd
argument `FTC_Cache  cache' to fit FTC_Node_CompareFunc
prototype.
* src/cache/ftcglyph.c (FTC_GNode_Compare): Ditto. Anyway,
`cache' is not used by its child ftc_gnode_compare().
diff --git a/src/cache/ftcglyph.c b/src/cache/ftcglyph.c
index fb825d4..52a7933 100644
--- a/src/cache/ftcglyph.c
+++ b/src/cache/ftcglyph.c
@@ -80,9 +80,10 @@
 
   FT_LOCAL_DEF( FT_Bool )
   FTC_GNode_Compare( FTC_GNode   gnode,
-                     FTC_GQuery  gquery )
+                     FTC_GQuery  gquery,
+                     FTC_Cache   cache )
   {
-    return ftc_gnode_compare( FTC_NODE( gnode ), gquery, NULL );
+    return ftc_gnode_compare( FTC_NODE( gnode ), gquery, cache );
   }
 
 #endif