core/parser: new internal msg flag - FL_UAC_AUTH

- to mark requests that had local uac authentication done (e.g., via
  uac_auth() from uac module)
- it is an indication that cseq should be increased

parser/msg_parser.h

@@ -123,6 +123,7 @@ typedef enum request_method {
 #define FL_RPL_SUSPENDED     (1<<16)  /* for async reply processing */
 #define FL_BODY_MULTIPART    (1<<17)  /* body modified is multipart */
 #define FL_RR_ADDED          (1<<18)  /* Record-Route header was added */
+#define FL_UAC_AUTH          (1<<19)  /* Proxy UAC-like authentication */
 
 /* WARNING: Value (1 << 28) is temporarily reserved for use in kamailio call_control
  * module (flag  FL_USE_CALL_CONTROL )! */