o All numeric integrators

      - Change way integrators are registered: Old method involves ROOT function call that assumes gROOT exist
        leading to static initialization order fiasco. New method registers initializer functions with
        RooNumIntFactory that will perform actual initialization when factory is used for the 1st time


   o RooNumIntConfig

      - Add methods registerInitializerFunction() to allow registration of initializer functions for
        each numeric integrator engine that exists

      - Add processInitializers() method to process registration of numeric integrators. Call this
        function in get/set/createProtoIntegrator().

      - Move static pointer to singleton instance inside instance() function so that initialization
        to zero is guaranteed when instance() code is executed


   o RooNumIntConfig

      - Move static pointer to default instance inside default() function so that initialization
        to zero of pointer is guaranteed when default() code is executed


   o RooIntegrator1D

     - Add configuration option 'extrapolation' that allows to switch off wynn-epsilon extrapolation
       and calculate error the simple way (difference in result between last two iterations).
       Default remains extrapolation on.


   o RooProdPdf

      - Change named argument constructor to be less confusing. Constructor now takes name,title and
        const RooArgSet& with regular PDFs followed by zero or more Conditional() arguments that
        specificy conditional PDFS


   o RooGlobalFunc

      - Remove global functions Partial() and Full(), add Conditional()



   o RooProdGenContext

      - Follow changes in RooProdPdf


git-svn-id: http://root.cern.ch/svn/root/trunk@11139 27541ba8-7e3a-0410-8455-c3a389f83636