on some platforms that lacked shared library support in the past. The
list hasn't been maintained at all and the gain is very limited, so just
get rid of it.
- assume that Python 2.4 and 2.5 are compatible and allow checking for
fallout.
- remove PYTHON_VERSIONS_COMPATIBLE that are obsoleted by the 2.3+
default. Modify the others to deal with the removals.