Fix https://sft.its.cern.ch/jira/browse/ROOT-6606
A call to InitializeGraphics is needed in TCanvas:Draw() in case the canvas comes from a file.
The previous attempt to fix it in TSystem::Load was wrong.
Copy from 5.34 fixes for a warning
Add a const version of TAxis::FindBin for backward compatibility after having added a const and non-const version of  TH1::GetAxis()
Remove assert. Fix for ROOT-6664
Check for the proxy w/o relying on name

which makes the check even more powerful: we now do not check for
mother classes not only for stl collections but also for all proxied
collections.
This is perfectly consistent with the concept of collection proxy,
which is there exactly to abstract from the details of the container
and focus on the contained entities.
Make the THttpServer::ProcessRequest() method virtual
In CheckSum properly handle the 'signed char' in the Reflex case.

gccxml was illegally replacing signed char with char ... so for the checksum equivalency, we need
to do the same (only in the emulate-reflex modes)
Add note about race condition
Also fwd declare types nested in namespaces.
Analyze and fwd declare all dependencies (ROOT-6705 ROOT-6719 ROOT-6712 ROOT-6695).
Fix mem corruption: iterator might be invalidated by insertion.
Silence enum typed/untyped redecl until fwd decl can handle it.
Fix position of "inline" in "inline namespace" (MacOS G__MathCore failure).
Silence warning.
Write function fwd decls! Follow DeclRefExpr template args.
Don't const_cast to ... const
Do not display suggestions only for ROOT.
Fix: https://sft.its.cern.ch/jira/browse/ROOT-6658
Thanks Bertrand.
Fix ROOT-6724: remove header inclusions in favour of fwd decls.
Coding conventions.