Fix loss of optimization of array iteration due to inlining

Fix loss of optimization of array iteration due to inlining

This helps loop-invariant motion to hoist complicated offset computations.

gcc/ada/
	* gcc-interface/trans.c (language_function): Add comment.
	(loop_info_d): Add fndecl and invariants fields.
	(find_loop_for): Test fndecl instead of the context of var.
	(find_loop): New function.
	(Regular_Loop_to_gnu): Fold back into...
	(Loop_Statement_to_gnu): ...this.  Emit invariants on entry, if any.
	(gnat_to_gnu) <N_Selected_Component>: Record nonconstant invariant
	offset computations in loops when optimization is enabled.
	* gcc-interface/utils2.c (gnat_invariant_expr): Handle BIT_AND_EXPR.
gcc/testsuite/
	* gnat.dg/opt93.ads, gnat.dg/opt93.adb: New test.