Introduce a simplified version of the Event example (libEventMT.so EventMT.cxx...

Introduce a simplified version of the Event example (libEventMT.so EventMT.cxx and EventMT.h) suitable to use with multiple thread or in the cases where more than one Event objects is needed at once. 
Event.h defines a singleton Event object while EventMT.h defines Event objects that are completely independent of each other.


git-svn-id: http://root.cern.ch/svn/root/trunk@34689 27541ba8-7e3a-0410-8455-c3a389f83636