* man/login.defs.d/SUB_GID_COUNT.xml: Document newusers behavior
when the user already have subordinate group IDs.
* man/login.defs.d/SUB_UID_COUNT.xml: Likewise.
* man/login.defs.d/SUB_GID_COUNT.xml: Fix typo (MAX<->MIN).
* man/login.defs.d/SUB_UID_COUNT.xml: Likewise.