Fix non-specific error message.

"something has gone wrong" is not helpful. Make this elog()
consistent with the other one in the same function.

Discussion: http://postgr.es/m/CA+Tgmoa_AZ2jUWSA_noiqOqnxBaWDR+t3bHjSygZi6+wqDBCXQ@mail.gmail.com

src/backend/postmaster/auxprocess.c

@@ -81,7 +81,7 @@ AuxiliaryProcessMain(AuxProcType auxtype)
 			MyBackendType = B_WAL_RECEIVER;
 			break;
 		default:
-			elog(ERROR, "something has gone wrong");
+			elog(PANIC, "unrecognized process type: %d", (int) MyAuxProcType);
 			MyBackendType = B_INVALID;
 	}