Bumping CMake minimum to 2.8.8 as agreed

This was discussed on the mailing list a few months ago.

Change-Id: I9a7d81fd3fb94827b1eab9f2e21ef965b05ebb09
Merge topic 'bump-cmake-requirement' into master

eee9f52c Bumping CMake minimum to 2.8.8 as agreed