Windows installer appends paths too far back in PATH

[larsv]

After installing the 2009.2.0.1 platform on Windows, my system %PATH% contains from the middle to the end the following:

C:\Program Files (x86)\Haskell Platform\2009.2.0\ghc-6.10.2\bin;C:\Program Files (x86)\Haskell Platform\2009.2.0\extralibs\bin;C:\Program Files (x86)\Haskell Platform\2009.2.0.1\bin;C:\Program Files (x86)\Haskell Platform\2009.2.0.1\extralibs\bin;C:\Program Files (x86)\Haskell\bin

As can be seen, the path to 2009.2.0.1 is after the path to 2009.2.0 which I had installed beforehand. This is likely related to the path appending changes in #25 and #37.

[refold]

The issue of having several HP versions installed side-by-side wasn't given much thought. This will be taken care of in the course of fixing #63.