[Ada] Build in place for nonlimited types

[Pierre-Marie de Rodat <derodat at adacore dot com>]

First cut at build-in-place for nonlimited types.
This is a work in progress; the build-in-place
support is currently disabled.

Tested on x86_64-pc-linux-gnu, committed on trunk

2017-09-29  Bob Duff  <duff@adacore.com>

	* exp_ch6.adb (Expand_Call_Helper): Handle case of build-in-place
	functions returning nonlimited types. Allow for qualified expressions
	and type conversions.
	(Expand_N_Extended_Return_Statement): Correct the computation of
	Func_Bod to allow for child units.
	(Expand_Simple_Function_Return): Remove assumption that b-i-p implies
	limited (initialization of In_Place_Expansion), and implies >= Ada
	2005.
	(Is_Build_In_Place_Result_Type): New function to accompany
	Is_Build_In_Place_Function and Is_Build_In_Place_Function_Call, because
	sometimes we just have the type on our hands, not the function.  For
	now, does the same thing as the old version, so build-in-place is
	disabled for nonlimited types, except that you can use -gnatd.9 to
	enable it.
	* exp_ch6.ads (Is_Build_In_Place_Result_Type): New function to
	accompany Is_Build_In_Place_Function and
	Is_Build_In_Place_Function_Call, because sometimes we just have the
	type on our hands, not the function.
	(Make_Build_In_Place_Call_In_...): Handle nonlimited build-in-place
	cases.
	(Make_Build_In_Place_Call_In_Object_Declaration): Remove the
	questionable code at the end that was setting the Etype.
	* exp_aggr.adb (Is_Build_In_Place_Aggregate_Return): New function to
	determine whether "return (...agg...);" is returning from a
	build-in-place function.
	(Initialize_Ctrl_Array_Component, Initialize_Ctrl_Record_Component):
	Remove assumption that b-i-p implies limited (initialization of
	In_Place_Expansion).
	(Build_Record_Aggr_Code): AI-287: fix comment; it can't be wrapped in
	an unchecked conversion.  Add assertions.
	(Convert_Aggr_In_Object_Decl): Establish_Transient_Scope -- no need for
	secondary stack here, just because the type needs finalization.  That
	code is obsolete.
	(Convert_To_Assignments): Only set Unc_Decl if Nkind (N) = N_Aggregate.
	For "return (...agg...);" don't assume b-i-p implies limited.
	Needs_Finalization does not imply secondary stack.
	(Expand_Array_Aggregate): Named notation.  Reverse the sense of
	Component_OK_For_Backend -- more readability with fewer double
	negatives.
	* exp_attr.adb (Expand_N_Attribute_Reference): Remove assumptions that
	b-i-p implies >= Ada 2005.
	* exp_ch3.adb (Expand_N_Object_Declaration): Remove assumptions that
	b-i-p implies >= Ada 2005.  Remove Adjust if we're building the return
	object of an extended return statement in place.
	* exp_ch4.adb (Expand_Allocator_Expression, Expand_N_Indexed_Component,
	Expand_N_Selected_Component, Expand_N_Slice): Remove assumptions that
	b-i-p implies >= Ada 2005.
	* exp_ch5.adb (Expand_N_Assignment_Statement): Remove assumption that
	b-i-p implies >= Ada 2005.
	* exp_ch7.adb: Comment fix.
	* exp_ch8.adb (Expand_N_Object_Renaming_Declaration): Remove
	assumptions that b-i-p implies >= Ada 2005.
	* exp_disp.adb (Expand_Interface_Actuals): Remove assumptions that
	b-i-p implies >= Ada 2005.
	* exp_util.adb (Build_Allocate_Deallocate_Proc): Look at Storage_Pool
	(Expr), in case Pool_Id is not set.
	(Initialized_By_Aliased_BIP_Func_Call): Handle case where the call is
	qualified or converted.
	(Is_Secondary_Stack_BIP_Func_Call): Don't check if Nkind (Selector_Name
	(Param)) = N_Identifier; that's all it could be.
	* sinfo.ads: Comment fixes.
	* snames.ads-tmpl: Comment fixes.
	* debug.adb: Add flag gnatd.9, to enable the build-in-place machinery.

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