Deletes a user setting's lock from the setting privilege lock.
	Note: by default, a process not running in a console environment
	is locked with a user lock.  A user_sets_unlock is required to
	unlock the process for settings.
	For settings to occur via dio_... calls dio settings must also be
	enabled with dio_enable_settings.

	N.B.: This routine just decrements the lock value so if it is
	already unlocked, i.e., 0, it will decrement to -1 and result in
	settings being locked.

	This function requires the following include files:


	Related functions:

	user_sets_lock, user_sets_lock_read, dio_enable_settings,

	C/C++ usage:

	int num_user_locks = user_sets_lock_read();
	// Only unlock if locked, because if you unlock when you're not locked,
	// you become locked.
	if (num_user_locks > 0)