Modern CMake usage: bump minimal version to 2.8.12.

CMakeLists.txt

@@ -23,7 +23,7 @@
 #   DEALINGS IN THE SOFTWARE.
 #
 
-cmake_minimum_required(VERSION 2.8.9)
+cmake_minimum_required(VERSION 2.8.12)
 project(Magnum)
 
 # CMake policies: enable MACOSX_RPATH by default

README.md

@@ -94,7 +94,7 @@ Minimal dependencies
     On Windows you can also use **MinGW-w64**. GCC 4.6, 4.5, 4.4 and MSVC 2013
     support involves some ugly workarounds and thus is available only in
     `compatibility` branch.
-*   **CMake** >= 2.8.9
+*   **CMake** >= 2.8.12
 *   **Corrade** - Plugin management and utility library. You can get it at
     https://github.com/mosra/corrade.
 

doc/building.dox

@@ -37,7 +37,7 @@ Minimal set of tools and libraries required for building is:
     On Windows you can also use **MinGW-w64**. GCC 4.6, 4.5, 4.4 and MSVC 2013
     support involves some ugly workarounds and thus is available only in
     `compatibility` branch.
--   **CMake** >= 2.8.9
+-   **CMake** >= 2.8.12
 -   **Corrade** - Plugin management and utility library. See
     @ref building-corrade "Corrade download and installation guide" for more
     information.