Fix for changes done with the vc merge:

 - Add a Scalar typedef definition in the TVectors  in order to use the ROOT::Math::VectorUtil functions
 - Fix a bug introduced in the Choleski decomposition for making it compiling with Vc. This fixes the testInversion test
Wrong y for a top-level window - in cocoa it's different, it not top-left, but bottom-left corner.
Fixed a a number of CMake issues. Adapted to new rescission of llvm/cling
Added option 'all' to switch on all optional components.
upgrade to Pythia8 >= 8180. Previous versions don't compile with latest clang.
show full compiler invocation (easier to later copy/paste in case of problems).
fix for ROOT-5573
Try to fix compiling warning on Vc on old gcc versions (less than 4.5)
Capture non-functions in caller insted of passing 0; add assert against 0.
Fix http://root.cern.ch/phpBB3/viewtopic.php?f=3&t=17054&p=73075#p73075