Patch by Brian Gallew for DG/UX. I'm not quite sure what it does but

Patch by Brian Gallew for DG/UX.  I'm not quite sure what it does but
it seems harmless for other platforms.  It plays tricks with the name
of the library used to link with.  Apparently DG/UX really wants a
shared library to link with if it wants shared modules to use symbols
from the library.  I'm not sure why this wasn't an issue with 1.4;
DG/UX seems to be the only platform where moving to a single library
made things harder!

BTW This adds a target to create libpython$(VERSION).so; however this
target is *only* for DG/UX.