bdist_wininst attempts to use the correct MSVC runtime
for the current version of Python.  This doesn't work
correctly when --target-version is set.  In that case,
bdist_wininst still uses the *current* sys.version (ie,
2.4) rather than the version specified as
--target-version.  Thus, the msvc7 runtime based
executable stub is *always* used.

This patch "hard-codes" knowledge of earlier Python
versions, providing the correct result when Python 2.4
is used to build Python 2.3 and earlier distributions.

As the comments in the patch mention, another
alternative is to allow --target-version to specify a
Python executable instead of a simple version string,
and execute that Python to parse its sys.version.  Let
me know if you think that is a good/better idea.

Assigning to Thomas for review, then please assign back.