[Ada] Missing dereference in bound of slice in element iterator

[Ada] Missing dereference in bound of slice in element iterator

2019-12-12  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_ch5.adb: (Analyze_Iterator_Specification): If the
	iteration is over a slice, complete the resolution of its
	bounds, which may be aebitrary expressions. The previous
	pre-analysis may have created itypes for the slice but has not
	performed the expansion that for example may introduce actions
	that specify explicit dereferences and run-time checks.

From-SVN: r279302