[Ada] Extended traversal subprograms for GNATprove

[Ada] Extended traversal subprograms for GNATprove

GNATprove needs traversal subprograms that do not simply traverse
syntactic nodes like Atree.Traverse_Func and Atree.Traverse_Proc, but
also traverse semantic nodes which are logically children of the nodes.
Now available through Sem_Util.Traverse_More_Func and
Sem_Util.Traverse_More_Proc.

There is no impact on compilation.

2019-08-12  Yannick Moy  <moy@adacore.com>

gcc/ada/

	* sem_util.adb, sem_util.ads (Traverse_More_Func,
	Traverse_More_Proc): New traversal subprograms.

From-SVN: r274284