Support for New Session, Duplicate Session and the Saved Sessions

submenu in Unix PuTTY, and Duplicate Session also in pterm. You do
_not_ want to know how this is done. Be warned.

[originally from svn r3110]

unix/ptermm.c

@@ -9,6 +9,7 @@
 
 const char *const appname = "pterm";
 const int use_event_log = 0;	       /* pterm doesn't need it */
+const int new_session = 0, saved_sessions = 0;   /* or these */
 
 Backend *select_backend(Config *cfg)
 {