Python on UNIX now trusts PYTHONHOME unconditionally
Modules/getpath.c:
Landmark changed to os.py.
Setting PYTHONHOME now unconditionally sets sys.prefix
(and sys.exec_prefix). No further checks are done whether the
standard lib can be found in that location or not. This is in
sync with the PC subdir getpath implementations.
PC/getpathp.c:
Landmark changed to os.py.
PC/os2vacpp/getpathp.c:
Landmark changed to os.py.
Note: BAW's checkin on exceptions.c eliminates earlier concerns about
a bogus PYTHONHOME value leading to a core dump. Instead it causes a
useless sys.path and prevents imports.
