ada: Make Sem_Util.Is_Aliased_View predicate more robust

ada: Make Sem_Util.Is_Aliased_View predicate more robust

The predicate implements the rules of the language so it needs to cope with
constructs rewritten by the expander, in particular explicit dereferences
that the expander uses liberally for various purposes.

This change makes the detection of rewritten calls more robust, plugging an
existing loophole for specific objects and exposing a missing propagation of
the Is_Aliased flag for certain build-in-place objects, as well as adds the
detection of rewritten return objects.

It also contains a small enhancement to Set_Debug_Info_Defining_Id aimed at
making it easier to debug the generated code by means of -gnatD.

gcc/ada/

	* sem_util.ads (Set_Debug_Info_Defining_Id): Adjust comment.
	* sem_util.adb (Is_Aliased_View) <N_Explicit_Dereference>: Return
	false for more artificial dereferences generated by the expander.
	(Set_Debug_Info_Defining_Id): Set Debug_Info_Needed unconditionally
	in -gnatD mode.
	* exp_ch6.adb (Replace_Renaming_Declaration_Id): Also preserve the
	Is_Aliased flag.