Change MSGHANDLER from compile-time to sysconf

include/config.h

@@ -641,12 +641,6 @@ typedef unsigned char uchar;
  * at least 28 additional rows beneath the status window on your terminal  */
 /* #define TTY_PERM_INVENT */
 
-/* NetHack will execute an external program whenever a new message-window
- * message is shown.  The program to execute is given in environment variable
- * NETHACK_MSGHANDLER.  It will get the message as the only parameter.
- * Only available with POSIX_TYPES, GNU C, or WIN32 */
-/* #define MSGHANDLER */
-
 /* enable status highlighting via STATUS_HILITE directives in run-time
    config file and the 'statushilites' option */
 #define STATUS_HILITES         /* support hilites of status fields */

include/sys.h

@@ -15,6 +15,7 @@ struct sysopt {
     char *shellers;   /* like wizards, for ! command (-DSHELL); also ^Z */
     char *genericusers; /* usernames that prompt for user name */
     char *debugfiles; /* files to show debugplines in. '*' is all. */
+    char *msghandler;
 #ifdef DUMPLOG
     char *dumplogfile; /* where the dump file is saved */
 #endif