Set exact boolean value to color property

This is a regression since 48e9e5f4
diff --git a/src/fcfreetype.c b/src/fcfreetype.c
index 9c2ae83..cd8fa43 100644
--- a/src/fcfreetype.c
+++ b/src/fcfreetype.c
@@ -1294,7 +1294,7 @@
 	if (!FcPatternObjectAddBool (pat, FC_OUTLINE_OBJECT, has_outline))
 	    goto bail1;
 
-	has_color = FT_HAS_COLOR (face);
+	has_color = !!FT_HAS_COLOR (face);
 	if (!FcPatternObjectAddBool (pat, FC_COLOR_OBJECT, has_color))
 	    goto bail1;