spark_xrefs.ads (Scope_Num): type refined to positive integers.

spark_xrefs.ads (Scope_Num): type refined to positive integers.

2016-06-22  Arnaud Charlet  <charlet@adacore.com>

	* spark_xrefs.ads (Scope_Num): type refined to positive integers.
	* lib-xref-spark_specific.adb (Detect_And_Add_SPARK_Scope):
	moved into scope of Collect_SPARK_Xrefs.
	(Add_SPARK_Scope): moved into scope of Collect_SPARK_Xrefs;
	now uses Dspec and Scope_Id from Collect_SPARK_Xrefs.
	(Collect_SPARK_Xrefs): refactored to avoid retraversing the list
	of scopes.
	(Traverse_Compilation_Unit): refactored as a generic procedure.
	* types.ads (Unit_Number_Type): range refined.

From-SVN: r237690