zfs: bump to 0.6.1, fix or cope with weirdnesses in its install

There are some hacky things I had to do to deal with how zfs
comes in two very closely intertwined packages, and the exact
same version of both packages have to be installed at the same
time.

The install scripts within the packages also have some high weirdnesses
where they try to install stuff within their own build directory.
Fortunately they're using standard autoconf makefiles so this can
be worked around by abusing DESTDIR so that doesn't happen.  I'm
not the biggest fan of doing it that way, but at least it seems to work.
Merge pull request #45 from dagbrown/master

zfs: bump to 0.6.1, and build improved (albeit not exactly clean)