Add version to shared phobos library name
Add the usual so simlinks for the shared Phobos lib.
Set the static lib as the default lib for the unittests.

The unittests will fail if they are linked with the shared lib, and the
shared lib is not in a path where ld will look for it when running the
executable.

Alternatively we could use the -rpath flag to add the directory
containing the newly build shared lib to the ld search path for the
unittests.