ada: Add rule check for call arguments

ada: Add rule check for call arguments

Implement SPARK RM 6.9(18).

If an assignment to a part of a ghost variable occurs in a ghost entity,
then the variable should be assertion-level-dependent on this entity.
[This includes both assignment statements and passing a ghost variable as an
out or in out mode actual parameter.]

gcc/ada/ChangeLog:

	* ghost.adb (Check_Procedure_Call_Levels): New function for
	implementing the check.
	* ghost.ads (Check_Procedure_Call_Levels): Likewise.
	* sem_ch6.adb (Analyze_Procedure_Call): Check the levels after
	the call has been resolved and the previous ghost region has
	been restored.