Add new flag --disable-x11 to build without X11 libs for batch only

environments (or systems without X11 like iOS).
The flag --minimal builds without X11 now. The new flag --gminimal builds
like --minimal but with X11. On Win32 we always build with basic graphics.


git-svn-id: http://root.cern.ch/svn/root/trunk@34578 27541ba8-7e3a-0410-8455-c3a389f83636