Python3.8 Windows DLL loading

[pepone]

Python 3.8 changes the way that extension DLLs are resolved, this affects the 3.8 source build, our pip builds still works

Toblerity/Fiona#851
https://bugs.python.org/issue36085

As this only affects the source builds, I think the simpler will be fto copy the dependencies next to the IcePy.d extension

[pepone]

A second option will be to call os.add_dll_directory before the call to import IcePy in

ice/python/python/Ice/__init__.py

Line 42 in 3f5d79a

import IcePy

The second option will require to add some logic to detect if we are running from a source distribution and locate the C++ bin directory.

Copying the dependencies seems simpler to me