cmake: Update to 2.8.11.2

The changelog is available at:
http://www.cmake.org/files/v2.8/CMakeChangeLog-2.8.11

I had to create a new patch from scratch, that's why it contains a lot
of differences. CMake developers has rewritten the files
(Modules/Platform/Linux.cmake and Modules/Platform/UnixPaths.cmake) to
comply to their coding style requirements and a lot of elements has
switched from upper to lower case.

Also, the previous patch partially consisted of commenting some
instructions mixed with line removals whereas mine is directlty
removing them in order to avoid useless evaluations and parsing in
resulting files.
Merge pull request #758 from bbenoist/cmake-update

cmake: Update to 2.8.11.2