[Ada] Alignment clause ignored on completion derived from private type

[Ada] Alignment clause ignored on completion derived from private type

2020-06-04  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* exp_attr.adb (xpand_N_Attribute_Reference) <Input>: Call
	Find_Inherited_TSS to look up the Stream_Read TSS.
	<Output>: Likewise for the Stream_Write TSS.
	* exp_ch7.adb (Make_Final_Call): Call Underlying_Type on
	private types to account for underlying full views.
	* exp_strm.ads  (Build_Record_Or_Elementary_Input_Function):
	Remove Use_Underlying parameter.
	* exp_strm.adb (Build_Record_Or_Elementary_Input_Function):
	Likewise and adjust accordingly.
	* exp_tss.adb (Find_Inherited_TSS): Deal with full views.
	Call Find_Inherited_TSS recursively on the parent type if
	the base type is a derived type.
	* sem_ch13.adb (Analyze_Attribute_Definition_Clause): Take
	into account underlying full views for derived types.
	* sem_ch3.adb (Copy_And_Build): Look up the underlying full
	view only for a completion.  Be prepared for private types.
	(Build_Derived_Private_Type): Build an underlying full view
	for a completion in the general case too.