Made a `no-cbits` branch that removes several things that use C code and
the FFI. I moved one of them out to a new haskell library,
<http://hackage.haskell.org/package/mountpoints>. Others were replaced with
other existing libraries. This will simplify git-annex's build process, and
more library use is good. Planning to merge this branch in a week or two.

v6 unlocked files don't work on Windows. I had assumed that since the build
was succeeding, the test suite was passing there. But, it turns out the
test suite was failing and somehow not failing the build. Have now fixed
several problems with v6 on Windows. Still a couple test suite problems to
address.
