With the automatic coloring options (PMC, PLC etc ...) it was easy to forget to add a drawing option.

This is now fixed. The issue was mentioned  here: https://sft.its.cern.ch/jira/browse/ROOT-9552

* Add the possibility to draw filled areas in NDC as requested here: https://sft.its.cern.ch/jira/browse/ROOT-9523

* Rel notes update

* - resolve conflict

* - typo

* resolve conflict

* - resolve conflict

Not in all classes R was proper placed.
Show title of RCanvas

Only compilation is fixed, no idea if performance measurements with
valgrind still works

* Implement ConstAdd, ConstMult, ReciprocalElementWise, SquareElementWise, SqrtElementWise in CPU, GPU and Reference architectures.

* Add Unit Tests for them in CPU, GPU architecture.

* Add ROOT Style docs and clang format the code.

Update the Fill() documentation according to the suggestion done here: https://root-forum.cern.ch/t/show-overflow-in-last-bin-of-histogram/29705/5

We need to move LLVM in ROOT to use the new behavior of policy CMP0051
as it will be removed soon and the warning below will become an error:

CMake Deprecation Warning at interpreter/llvm/src/CMakeLists.txt:15 (cmake_policy):
  The OLD behavior for policy CMP0051 will be removed from a future version
  of CMake.

  The cmake-policies(7) manual explains that the OLD behaviors of all
  policies are deprecated and that a policy should be set to OLD only under
  specific short-term circumstances.  Projects should be ported to the NEW
  behavior and not rely on setting a policy to OLD.

When Davix is not builtin to ROOT, it's not necessary to propagate
link dependencies on Libxml2 and OpenSSL.

 * PyROOT_PyUnicode_AsString changed return type from char* to const char*
 * Using _PyObject_GC_TRACK results in linking error:
   undefined reference to `_PyGC_generation0'
   The python documentation says this about _PyObject_GC_TRACK:
   "A macro version of PyObject_GC_Track(). It should not be used for
   extension modules."
   So it should not be used. Calling PyObject_GC_Track instead avoids the
   undefined symbol. I also removed the #ifndef R__WIN32 since the
   comment indicates that this was added to avoid the same issue on
   windows. Calling PyObject_GC_Track instead of using the
   _PyObject_GC_TRACK macro should fix the undefined symbol probelem on
   windows too.

* Implement Base Class VOptimizer

* Implement Class TSGD with Momentum method

* Add Unit Tests for TSGD

* Add Parsing Options for Optimizers

* Modify MethodDL to include the optimizer TSGD

* Add ROOT Style docs and clang-format the code

On certain Windows builds, `return {..., true}` would create a local SequencePtr, return a copy, then destruct the local - which in turn would delete fSequence. Instead, move the local and remember that the local has lost ownership.

This patch fixes a few recent runtime_cxxmodules failures.