Update CMake to 3.0.1.
The 3.0 series is an incremental improvement over the previous 2.8 series
despite the major version number change. A list of important changes is
available at http://www.cmake.org/cmake/help/v3.0/release/3.0.0.html
On the porting side
* The minimum FreeBSD release we have to support in the ports tree is now
recent enough that ports/168671 can finally be committed: instead of
building and using CMake's own copies of bzip2, curl, expat, libarchive,
liblzma and zlib, we use the versions in ports and/or the base system.
* CMake's documentation system has been changed and vastly improved at the
cost of now depending on Sphinx. We still generate only man pages, but can
start generating the HTML documentation in the future if desired.(Only the first 15 lines of the commit message are shown above )