- modify matrix expression to use both i and j index. This improves substuntially multiplication and transpose operations where there is no need to calculate the right offset for each element
- use a static const function in MatRepSym for the offset as suggested by Vincenzo. This gives some small improvements on Windows and Solaris
- generate dictionary also for the MatRepStd classes


git-svn-id: http://root.cern.ch/svn/root/trunk@14197 27541ba8-7e3a-0410-8455-c3a389f83636