added IRETQ

Author: leitimmel

spec/iasm.dd

@@ -730,6 +730,7 @@ $(H2 $(LNAME2 supported_opcodes, Opcodes Supported))
         , $(TT invlpg)
         , $(TT iret)
         , $(TT iretd)
+        , $(TT iretq)
         )$(TROW $(TT ja)
         , $(TT jae)
         , $(TT jb)