Buildsystem/CMake: Fix an issue with MSVC not finding git-binary when updating the revisionhash/revisiondate + rename DISABLEGITCHECK parameter to WITHOUT_GIT (to adhere to our standard)
Also cleaned up the checks slightly + moved git-specific testing to its own macro (minor changes to shaurens original patch applied)
Buildsystem/CMake: Forgot to change variable in main CMakeLists.txt
Buildsystem/CMake: Correct a few mistakes regarding WITHOUT_GIT, and add a better warning during configure-phase.
Buildsystem: Do not print warning that user needs to do a git pull with tags if configured to not use git at all
Scripts/Icecrown Citadel: Fixed possible crash for Necrotic Plague (if cast outside of ICC)

Closes #9188