Removed major memory-inefficiency from MaHashIndex!

[Chris Muller]

An "optimization" in MaHashIndex traded way too much memory
consumption just to avoid two Array allocations for each query of a
MaHashIndex.  This is way not worth it.

I strongly recommend installing/merging Ma special collections-cmm.85
from the "MagmaTester" project of squeaksource.  This will be rolled
into release 41, of course.

 - Chris