Support for Python 3.0, drop support for pre-2.0.

Support for Python 3.0, drop support for pre-2.0.

* lib/py-compile: Do not import string; use sys.stdout.write
instead of print, files.split instead of string.split.
* m4/python.m4 (AM_PATH_PYTHON): Also look for python3 and
phython3.0; do not look for python1.5.  Use sys.stdout.write.
(AM_PYTHON_CHECK_VERSION): Do not use string; adjust to xrange
removal in Python 3.0, and changed semantics of map.
* doc/automake.texi (Python, Hard-Coded Install Paths): Update
Python versions mentioned in the manual, using 2.5 everywhere.
* NEWS, THANKS: Update.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>