CheckerGccPlugins: Static checker fixes.
Don't ignore TGC names in naming checker:
The naming checker ignores classes starting with T' followed by an uppercase letter as being ROOT classes. However, this was ignoring ATLAS
TGC' classes.
Add `TGC' as an exception to this rule.
Don't ignore ctors/dtors:
The thread-safety checker was ignoring constructors and destructors. Fix.
Some fixes for const checking for function returns:
In this example:
int&
C::foo() const
{
int& svc [[gnu::thread_safe]] = const_cast<int&>(c);
return svc;
}
we were (a) crashing; and even once that was fixed, we were still emitting a const-discarded warning. Fixed both issues.