Debug regressions: use a plusarg to enable remote bitbang.

csrc/remote_bitbang.cc

@@ -69,6 +69,7 @@ remote_bitbang_t::remote_bitbang_t(uint16_t port) :
   trstn = 1;
   quit = 0;
 
+  printf ("This emulator compiled with JTAG Remote Bitbang client. To enable, use +jtag_rbb_enable=1.\n");
   printf("Listening on port %d\n",
          ntohs(addr.sin_port));
   fflush(stdout);