ada: GNAT-LLVM compiler crash on container aggregates with iterators

Recent fixes for container aggregates with iterated element associations
exposed a latent bug with loops that are wrapped in blocks, where the loop
entity's scope was not adjusted to reflect the new enclosing block scope.

gcc/ada/

	* sem_ch5.adb (Analyze_Loop_Statement.Wrap_Loop_Statement): Remove
	the loop Entity_Id from its old scope and insert it in the new
	block scope that wraps it.