* gcc-interface/gigi.h (enum standard_datatypes): Add new values
	ADT_sbitsize_one_node and ADT_sbitsize_unit_node.
	(sbitsize_one_node): New macro.
	(sbitsize_unit_node): Likewise.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Array_Subtype>: Fix
	latent bug in the computation of subrange_p.  Fold wider_p predicate.
	(cannot_be_superflat_p): Use an explicitly signed 64-bit type to do
	the final comparison.
	(make_aligning_type): Build real negation and use sizetype throughout
	the offset computation.
	(maybe_pad_type): Do not issue the warning when the new size expression
	is too complex.
	(annotate_value) <INTEGER_CST>: Simplify code handling negative values.
	* gcc-interface/misc.c (gnat_init): Initialize sbitsize_one_node and
	sbitsize_unit_node.
	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Pool_Address>: Fold
	double negation.
	(gnat_to_gnu) <N_Free_Statement>: Likewise.
	* gcc-interface/utils.c (convert): Use sbitsize_unit_node.
	* gcc-interface/utils2.c (compare_arrays): Compute real lengths and use
	constants in sizetype.  Remove dead code and tweak comments.  Generate
	equality instead of inequality comparisons for zero length tests.

From-SVN: r158461