Hi,
This attempts to fix Windows builds via NMake+distutils, in particular for Python 2.7.x (where, it seems that it is still supported), by moving up altImport() so that it can be properly referred to during the build.
This also drops the bits that tries to update the generated libxml2.py for libxslt, since it did seem to me that it is not supported to build the libxslt Python bits from the libxml2 Python bits at least on Windows.
With blessings, thank you!