[Ada] Handle iterator filters on loop specifications over containers

[Ada] Handle iterator filters on loop specifications over containers

gcc/ada/

	* sem_ch5.adb (Analyze_Iterator_Specification): If iterator
	filter is present, preanalyze filter without expansion.
	(Analyze_Loop_Parameter_Specification): When
	loop_Parameter_Specification is rewritten as
	Iterator_Specification, transfer Iterator_Filter if present.