Now --version prints something like "This is FreeRDP version 1.0.1 (git
1.0.1-710-g90ec2)". Having a git commit id helps to identify builds and eases
debuggin.
The downside is that GetGitRevisionDescription retriggers a cmake
re-configuration after each git commit. But thats the only way to get correct
version informations without having git hooks or similar.
GetGitRevisionDescription is based on Ryan Pavlik cmake Modules.
