* einfo.ads Update the usage of flag
	Uses_Sec_Stack. Uses_Sec_Stack now applies to E_Loop entities.
	* exp_ch5.adb (Expand_Iterator_Loop): The temporary for a cursor
	now starts with the letter 'C'. This makes reading expanded
	code easier.
	* exp_ch7.adb (Establish_Transient_Scope): Add local variable
	Iter_Loop. Signal that an Ada 2012 iterator loop requires
	secondary stack management when creating a transient scope for
	an element reference.
	* exp_util.adb (Process_Statements_For_Controlled_Objects):
	When wrapping the statements of a loop, pass the E_Loop entity
	to the wrapping machinery.
	(Wrap_Statements_In_Block): Add
	formal parameter Scop along with comment on usage. Add local
	variables Block_Id, Block_Nod and Iter_Loop. Mark the generated
	block as requiring secondary stack management when the block is
	created inside an Ada 2012 iterator loop. This ensures that any
	reference objects are reclaimed on each iteration of the loop.
	* sem_ch5.adb (Analyze_Loop_Statement): Mark the generated block
	tasked with the handling of container iterators as requiring
	secondary stack management. This ensures that iterators are
	reclaimed when the loop terminates or is exited in any fashion.
	* sem_util.adb (Add_Block_Identifier): New routine.
	(Find_Enclosing_Iterator_Loop): New routine.
	* sem_util.ads (Add_Block_Identifier): New routine.
	(Find_Enclosing_Iterator_Loop): New routine.

From-SVN: r208133