Improve Windows 7 detection during install

[choksi81]

seattleinstaller.py, lines 259 and following, claims to detect Windows 7 using

version = platform.release()
  if version == "Vista" or version == "post2008server":
    # ...

This doesn't always work. As far as I tested on my clean install of Windows 7 Professional (64 bit, German localization), version strings are:

|| '''Python version(s)''' || '''platform.release() string''' ||
|| 2.5.2 and 2.5.4 || Vista ||
|| 2.6.2 to 2.6.5 || post2008Server (note capitalization) ||
|| 2.6.6 and 2.7.0 to 2.7.3 || 7 ||

(See http://bugs.python.org/issue7863 for additional details.)

The lack of "7" and the wrong capitalization of "post2008Server" could be the reason that installing on Windows 7 sometimes fail. So, assuming that the startup behavior of Win7 didn't change over Windows Vista, line 260 of seattleinstaller.py needs to be changed to

if version == "Vista" or version == "post2008Server" or version == "7":

Obviously, the comment block above the statement should be fixed as well. If we were pedantic, the variable version should be renamed release to avoid the perceived name clash with the function platform.version().

Please drop me a line if I can go ahead with patching.

[aaaaalbert]

See also #146