[Core] [RFA/DWARF2] Handle nested subprograms in CU pc bound calculation

[Joel Brobecker]

> All information the compiler has available is inside the ppu and the debug 
> information is generated from it. We should simply place anything GDB 
> needs into the debug information.

OK.  Thanks to everyone who participated in the discussion. I pretty
much agree with the above.

Until then, I would suggest that we do not put the nested subprograms
in the global scope, as nested subprogram names might collide with
global functions that have the same name.  But if the Pascal users
feel differently, then it's easy to fix.

-- 
Joel