system-wide configuration file

Add options SYSCF (to add a system-wide configuration file) and SYSCF_FILE
(for a file-based implementation of SYSCF) - this allows a binary distribution
to be configured at install time.  The only option supported at this time is
WIZARDS - a list of usernames which can use -D; currently only for unix-likes
but should be extendable to anything that has a concept of multiple users.
Add mac tty multiuser config using sgid.

sys/unix/Install.unx

@@ -82,6 +82,16 @@
     a game that was in progress.  The recover command is installed in the
     HACKDIR by default.
 
+9.  If you specified SYSCF (and SYSCF_FILE) in config.h, create the file
+    defined as SYSCF_FILE and fill in any of the following values if you
+    wish to override the compiled-in defaults:
+	WIZARDS= a space-separated list of usernames who can use -D
+		If the first character is '*' then any user can use -D.
+    This is a standards config file, so blank lines and lines starting with
+    pound signs are ignored; while other, standard options (such as catname)
+    can be specified in this file, this is considered a bug and may be changed
+    in the future.
+
 Notes:
 
 1.  Save files and bones files from previous versions will not work with