This directory contains files that are commonly inherited by many different
objects in the mudlib. For example, object.c, room.c, and board.c are all
here. 
Files that are inherited by only a single object generally go in a
directory with the same name as the object that includes them, with
the .c removed. For example, /system/user.c inherits /system/user/login.c,
/system/player.c inherits /system/player/edit.c, and so forth.