ada: Accept aspects Global and Depends on abstract subprograms

Aspects Global and Depends are now allowed on abstract subprograms
(as substitutes for Global'Class and Depends'Class).

This patch implements the recently modified rules SPARK RM 6.1.2(2-3).
The behavior for Contract_Cases and aspects on null subprograms stays
as it was.


	* sem_prag.adb (Analyze_Depends_Global): Accept aspects on
	abstract subprograms.
1 file changed