poly_int: struct_value_size

This patch makes calls.c treat struct_value_size (one of the
operands to a call pattern) as polynomial.

2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* calls.c (emit_call_1, expand_call): Change struct_value_size from
	a HOST_WIDE_INT to a poly_int64.

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

From-SVN: r256162