ada: Add support for 'Object_Size to pragma Compile_Time_{Warning,Error}

ada: Add support for 'Object_Size to pragma Compile_Time_{Warning,Error}

With the same level as for 'Size, that is to say, full evaluation of the
boolean expressions it may be contained in and handling of private types.

gcc/ada/

	* sem_attr.adb (Analyze_Attribute) <Attribute_Size>: Remove special
	processing for pragma Compile_Time_{Warning,Error}.
	(Eval_Attribute.Compile_Time_Known_Attribute): Set Is_Static on the
	resulting value if In_Compile_Time_Warning_Or_Error is set.
	(Eval_Attribute.Full_Type): New helper function.
	(Eval_Attribute): Call Full_Type for type attributes.  Add handling
	of Object_Size and adjust that of Max_Size_In_Storage_Elements in
	the non-static case.