X11: Fix renaming at player selection

Due to the new player selection dialog I did, it was possible
to rename your character - but this didn't rename the lock files
and tried to load a save from the wrong name.

This is a bit of a hack, but seems to work and didn't seem to
cause problems for the tty.

include/flag.h

@@ -191,6 +191,7 @@ struct instance_flags {
      * behaviour of various NetHack functions and probably warrant
      * a structure of their own elsewhere some day.
      */
+    boolean defer_plname;  /* X11 hack: askname() might not set plname */
     boolean herecmd_menu;  /* use menu when mouseclick on yourself */
     boolean invis_goldsym; /* gold symbol is ' '? */
     int parse_config_file_src;  /* hack for parse_config_line() */