[Bf-committers] CMake minimum version increased to 3.0

[Campbell Barton]

Hi, Blender now depends on CMake 3.0 or later to build.
While there was no single urgent need to update, removing sorted-libs
kludge depends on it (see T46725).
There are various improvements we can make use of [1].

It also means we don't need to keep checking 2.8 compatibility when
making larger changes to the build-system.

[1]: https://cmake.org/cmake/help/v3.3/release/3.0.html

-- 
- Campbell