poly_int: fold_ctor_reference

poly_int: fold_ctor_reference

This patch changes the offset and size arguments to
fold_ctor_reference from unsigned HOST_WIDE_INT to poly_uint64.

2017-12-20  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* gimple-fold.h (fold_ctor_reference): Take the offset and size
	as poly_uint64 rather than unsigned HOST_WIDE_INT.
	* gimple-fold.c (fold_ctor_reference): Likewise.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r255869