to the AddEntry function was changed according to the fact that the

None -> null pointer conversion is no longer implemented in Cppyy

* Fix doxygen generation with Python 3

* Adjust tutorials for doxygen documentation generation.
When run inside the makeimage.py wrapper during doxygen generation the
variable scope is different than when the tutorials are run stand-alone.
The change in tutorials/math/tStudent.py is Python 3 specific and is due to
that list comprehensions in Python 3 are run in an implicit function scope.

* highlight mode for histogram or graph objects

* add animated gifs

* add doc for highlight mode

* renew hlHisto3_top.gif

Add tStudent.py to the list of math tutorials.

This reverts commit 21d726ba.
This change is platform dependent! Everything works on ubuntu16, but fails
on other platform. The change is reverted for 6.13, waiting to understand more
about this difference.

Tutorials should either rely on rootmaps and remove gSystem->Load(), or use R__LOAD_LIBRARY instead.

All tutorials calling gSystem->Load() have been been revisited as suggested here https://sft.its.cern.ch/jira/browse/ROOT-8938

Thanks to Alberto Ferro for these developments.

Remove some debug statement and add inclusion of C headers before including then inside an anonymous namespace

Remove from TRandom integer parameter in Rndm. No more Rndm(int)
Add new MixMax version (2.0) and use differentt N, N=240, N= 17 and include also mixmamx1.0 for N=256
Improve MixMaxEngine class by adding a template N and a decimation number S (which default = 0)
Implement also in library some TRandomGen based on std engines (Mersenne-Twister 64 and Ranlux 48).