First version which runs an install-script (specified by the
--install-script ... command line option to bdist_wininst) at the end
of the installation and at the start of deinstallation. Output
(stdout, stderr) of the script (if any) is displayed in the last
screen at installation, or in a simple message box at deinstallation.
sys.argv for the script will contain '-install' at installation
time or '-remove' at deinstallation time.
The installation script runs in an environment (embedded by the
bdist_wininst runtime) where an additional function is available as