Add the directory containing libxml2.dll with os.add_dll_directory to
make tests work on MinGW.
This has changed in Python 3.8 but for some reason, the issue only
turned up with Python 3.11 on MinGW. Contrary to documentation, copying
libxml2.dll into the directory containing the .pyd file doesn't work.
As per https://peps.python.org/pep-0394/, the python binary can be one
of the following options:
- Python 2
- Python 3
- Not exist
All of the scripts in libxml2 use 'python', which may not exist.
As Python 2 reached EOL on the 1st January 2020, it's safe to move the
scripts to use python3 explicitly.
* python/types.c python/tests/Makefile.am python/tests/xpathret.py:
added the possibility of returning nodesets from XPath extension
functions written in Python
Daniel