Fix co-array allocation

Fix co-array allocation

The Fortran front-end has a bug in which it uses "int" values for "size_t"
parameters.  I don't know why this isn't problem for all 64-bit architectures,
but GCN ends up with the data in the wrong argument register and/or stack slot,
and bad things happen.

This patch corrects the issue by setting the correct type.

2018-09-21  Andrew Stubbs  <ams@codesourcery.com>
            Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/fortran/
	* trans-expr.c (gfc_trans_structure_assign): Ensure that the first
	argument of a call to _gfortran_caf_register is of size_type_node.
	* trans-intrinsic.c (conv_intrinsic_event_query): Convert computed
	index to a size_type_node type.
	* trans-stmt.c (gfc_trans_event_post_wait): Likewise.

Co-Authored-By: Kwok Cheung Yeung <kcy@codesourcery.com>
From-SVN: r264468