Don't add a value for FC_FULLNAME in meta face

FC_FULLNAME is affected by variables and could be different
against it. FC_FULLNAME should be dropped from meta face.

Fixes https://gitlab.freedesktop.org/fontconfig/fontconfig/issues/185
diff --git a/src/fcfreetype.c b/src/fcfreetype.c
index 9691ba3..f2f5c04 100644
--- a/src/fcfreetype.c
+++ b/src/fcfreetype.c
@@ -1528,6 +1528,8 @@
 		    break;
 		case TT_NAME_ID_MAC_FULL_NAME:
 		case TT_NAME_ID_FULL_NAME:
+		    if (variable)
+			break;
 		    if (FcDebug () & FC_DBG_SCANV)
 			printf ("found full   (n %2d p %d e %d l 0x%04x)",
 				sname.name_id, sname.platform_id,