Do not rely on the declcontext order.
Put the describing headers next to the PCM, delete them afterwards.
Remove unused enum.
Refactor creation of PCM utility headers.
HandleNewDecl() only calls UpdateListOfMethods() for changed TClasses.

So always recreate the list of methods (of a changed TClass as determined by HandleNewDecl()).
Thus no need to check NMethod() because the content of TClingClassInfo and TClass will be identical as the updates are always happening, unconditionally.
Don't cache the value of NMethods().
Remove unused NMethods (var, function, cache)