[Ada] Misc cleanup related to finalization

[Ada] Misc cleanup related to finalization

This patch cleans up some code issues found while working on
finalization, and adds some debugging aids.

gcc/ada/

	* exp_ch7.adb: Change two constants Is_Protected_Body and
	Is_Prot_Body to be Is_Protected_Subp_Body; these are not true
	for protected bodies, but for protected subprogram bodies.
	(Expand_Cleanup_Actions): No need to search for
	Activation_Chain_Entity; just use Activation_Chain_Entity.
	* sem_ch8.adb (Find_Direct_Name): Use Entyp constant.
	* atree.adb, atree.ads, atree.h, nlists.adb, nlists.ads
	(Parent): Provide nonoverloaded versions of Parent, so that they
	can be easily found in the debugger.
	* debug_a.adb, debug_a.ads: Clarify that we're talking about the
	-gnatda switch; switches are case sensitive.  Print out the
	Chars field if appropriate, which makes it easier to find things
	in the output.
	(Debug_Output_Astring): Simplify. Also fix an off-by-one
	bug ("for I in Vbars'Length .." should have been "for I in
	Vbars'Length + 1 ..").  Before, it was printing Debug_A_Depth +
	1 '|' characters if Debug_A_Depth > Vbars'Length.