[Ada] ACATS 4.1G - C760A02 - Near infinite finalization

[Ada] ACATS 4.1G - C760A02 - Near infinite finalization

2020-06-19  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* exp_ch3.ads (Ensure_Activation_Chain_And_Master): New
	subprogram.
	* exp_ch3.adb (Ensure_Activation_Chain_And_Master): New
	subprogram that factorizes code.
	(Expand_N_Object_Declaration): Call new subprogram.
	* sem_ch6.adb (Analyze_Function_Return): Returning a
	build-in-place unconstrained array type defer the full analysis
	of the returned object to avoid generating the corresponding
	constrained subtype; otherwise the bounds would be created in
	the stack and a dangling reference would be returned pointing to
	the bounds.