Fixes to 4522 Minifig hammer

[N. W. Perry]

Is this difference big enough to make the old version obsolete?

Someone might have made a model where the mallet is placed standing on its head. 
Or one where the head strikes the surface of a pole/bar.

I think we need to make this 4522a.dat, and obsolete the old mallet.

Possibly, as the handle was also lengthened by 0.5 so that the overall length remains at 60 LDU.