moved windows binaries into a 'bin' subdirectory.

Related to #127. But this doesn't work just yet!

1. The packaging script needs to be checked that it packages the newly added `win32/bin' directory properly.
2. while testing I ran into a recent issue (couldn't find a link, but it was on the mailing list somewhere) that the `mkdir` only creates a single level, instead of a full tree. So that should probably be resolved first before integrating this PR.