sresolv: made sres_record_class static

Should never been global.

darcs-hash:20081215165706-db55f-f08bf1dbca145870b666e4ad88c6c638c7c3959c.gz

libsofia-sip-ua/sresolv/sres.c

@@ -1536,7 +1536,8 @@ char const *sres_record_type(int type, char buffer[8])
 }
 
 /** Convert class to its name. */
-char const *sres_record_class(int rclass, char buffer[8])
+static char const *
+sres_record_class(int rclass, char buffer[8])
 {
   switch (rclass) {
   case 1: return "IN";