Fix PR fortran/93671; ICE in reffing coarray alloc. comps.

Fix PR fortran/93671; ICE in reffing coarray alloc. comps.

Fix an ICE when in a coarray an allocatable component had another allocatable
component.

gcc/fortran/ChangeLog:

2020-08-10  Andre Vehreschild  <vehre@gcc.gnu.org>

	PR fortran/93671
	* trans-array.c (structure_alloc_comps): Keep caf-mode when applying to
	components; get the caf_token correctly for allocated scalar components.

gcc/testsuite/ChangeLog:

2020-08-10  Andre Vehreschild  <vehre@gcc.gnu.org>

	PR fortran/93671
	* gfortran.dg/coarray/pr93671.f90: New test.