Remove use of Cintex in ROOT6 macros

Cintex does not exist in ROOT6.  This pull request removes the loading of libCintex.so and the enabling of Cintex from ROOT macros in the ROOT6 IB, since libCintex.so does not exist in ROOT6.  The use of Cintex had previously been removed from other C++ code, but not from ROOT macros.
Please merge this request as soon as convenient.