The new TMinuit class can be made persistent and clonable.

The default constructor has been modified to correctly preset all
the pointers and initialize the structures only in case
TClass is not in read mode.
TMinuit.h has been modified with new data members used to indicate
the length of Minuit arrays.


git-svn-id: http://root.cern.ch/svn/root/trunk@6623 27541ba8-7e3a-0410-8455-c3a389f83636