poly_int: store_field & co

poly_int: store_field & co

This patch makes store_field and related routines use poly_ints
for bit positions and sizes.  It keeps the existing choices
between signed and unsigned types (there are a mixture of both).

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

gcc/
	* expr.c (store_constructor_field): Change bitsize from a
	unsigned HOST_WIDE_INT to a poly_uint64 and bitpos from a
	HOST_WIDE_INT to a poly_int64.
	(store_constructor): Change size from a HOST_WIDE_INT to
	a poly_int64.
	(store_field): Likewise bitsize and bitpos.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>
From-SVN: r255880