Add CHECK_PLNAME to sysconf

Setting CHECK_PLNAME to 1 makes WIZARDS, EXPLORERS, and SHELLERS
check the player name instead of the user's login name.

This is mostly useful for public servers which have external
login system and don't create user accounts for players.

doc/fixes36.1

@@ -179,6 +179,8 @@ X11: enable a scroll bar in menu windows
 X11: support pre-selected entries in menu windows
 X11: make the extended command menu be easier to use and look a little nicer
 X11: make the getline text entry widget display a bigger text entry area
+unix: add CHECK_PLNAME-option to sysconf to make WIZARDS, EXPLORERS, and
+	SHELLERS check player name instead of user's login name
 
 
 General New Features