Rework python module compile so it doesn't code the stagedir in it 
While here switch to USES=tar:bzip2
Remove waf from SHEBANG_FILES. it contains binary so running sed on it
not guaranteed to work as intended. 
Prefix waf commands with PYTHON_CMD so it run with the correct python version.
Use the waf --destdir command for destdir
Remove configure_ENV because they are already set.
Use post-patch to dynamicly fix the python version in test/examples_test.py
instead of a patch.
Reported by: swills@ , mva