[Ada] Crash processing sources under GNATprove debug mode

[Ada] Crash processing sources under GNATprove debug mode

Processing sources under -gnatd.F the frontend may crash on
an iterator of the form 'for X of ...' over an array if the
iterator is located in an inlined subprogram.

2018-07-16  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* exp_ch5.adb (Expand_Iterator_Loop_Over_Array): Code cleanup. Required
	to avoid generating an ill-formed tree that confuses gnatprove causing
	it to blowup.

gcc/testsuite/

	* gnat.dg/iter2.adb, gnat.dg/iter2.ads: New testcase.

From-SVN: r262707