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:
user_sets_lock, user_sets_lock_read, dio_enable_settings,
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)