Several fixes to testall for Windows.

- Add --bindir parameter. This is much more convenient than listing
  each tool separately, but the technical reason is that Windows
  requires all necessary DLLs to be in the same directory as the
  executable. Therefore we cannot merely copy each binary into the
  temporary workdir; we need to copy the whole bin directory.
- Remove unused --no-nova parameter.
- Different GAINROOT default for Windows.
- Use hardlinks on Windows (see comment for why).
- Remove shell IFS setting. It was added because it makes it easier
  to deal with paths with spaces in them, but I believe we have
  covered all those cases with quotes now, and IFS interferes with
  LN_CMD having a space followed by arguments in it.
Merge pull request #1440 from kacfengine/testall_on_windows

Several fixes to testall for Windows.