ada: Fix support for initialization of components in constructors

Enforce the following rule: If the component of a record type is of
a type that doesn't have a parameterless constructor, it has to be
initialized by one of these two mechanism: 1) through the default
value provided at component declaration, or 2) through an Initialize
aspect that can rely on constructor parameters.

Enforce the following rule: a constructor for a derived type whose
parent type needs construction and has no default parameterless
constructor must call the parent constructor through a Super aspect
to initialize its parent components.

Fix order of initialization of derived record type components.

gcc/ada/ChangeLog:

	* sem_ch6.adb (Constructor_Components_OK): New local subprogram of
	Analyze_Direct_Attribute_Definition. Checks performed when processing
	the body of a constructor.
	(Analyze_Direct_Attribute_Definition) <Name_Constructor>: Report an
	error on the body of a constructor for a derived type whose parent
	type needs construction and has no default parameterless constructor
	and has no Super aspect to initialize its parent components.
	* sem_ch7.adb (Inspect_Components_Needing_Construction): New local
	subprogram of Analyze_Package_Specification.
	(Inspect_Abstract_Constructors_Completion): Rename formal parameter.
	* exp_ch6.adb (Prepend_Constructor_Procedure_Prologue): Fix the order
	of initialization of record type components: parent components must
	be initialized first, then the own components following their
	declaration order.
	* sem_util.ads (First_Component_Declaration): New subprogram.
	* sem_util.adb (First_Component_Declaration): New utility subprogram
	that returns the first non-pragma non-inherited component declaration
	of a record type.