Transaction status is set twice based on moderate flag

Both userpoints_userpointsapi() and _userpoints_transaction() set status based on the moderate flag.

That was never necessary and now it's a bad idea because $params is passed to the hooks by reference which allows them to change status in the points before hook but it's overriden again after that.

Patch also makes sure that the constants are used instead of 0/1/2. Makes the code a lot easier to read especially since it's kinda backwards to use 0 for approved :)