ada: Use corect capacity with two dimensional arrays

ada: Use corect capacity with two dimensional arrays

Previously when a bounded list was initialized with an array aggregate
then we used the correct size only if the array was one dimensional.
This patch adds support for deriving the size for multidimensional array
types as well.

gcc/ada/ChangeLog:
	* exp_aggr.adb (Build_Siz_Exp): Support deriving the size of the
	container aggregate with multi-dimensional arrays. Make the
	function return an node of an expression instead of an integer.
	Additionally calculate the size expression for
	Component_Associations.
	(To_Int) make this method available for more functions.
	(Aggregate_Size) Relocate the calculation of
	Componenet_Associations to Build_Siz_Exp.