* src/usermod.c: Do not assign static to NULL.

	* src/usermod.c: Do not assign static to NULL.
	* src/usermod.c (date_to_str): buf needs to be unique (e.g.
	independent from negativ), and is an out buffer.
	* src/usermod.c: Ignore return value from snprintf, and force
	nul-termination of buffer.
	* src/usermod.c: Improve memory management.
	* src/usermod.c: An audit bloc was not reachable, moved above on
	success to move the home directory.
	* src/usermod.c: Ignore close() return value for the mailbox
	(opened read only).