* Remove download and build Boost from source and all CMake boost source build
dependencies.
* Make FindCairo.cmake use pkg-config when it's available not just all
platforms except windows.
* Add version checking to FindCairo.cmake.
* Change find GML version to 0.9.5.1 which is the current version in Ubuntu
14.04 LTS.
* Update required Cairo version to 1.12.1.