PR fortran/15326
	* trans-array.c (gfc_add_loop_ss_code): Set ss->string_length in
	the GFC_SS_FUNCTION case too.
	* trans-expr.c (gfc_conv_function_val): Allow symbols to be bound
	to function pointers as well as function decls.
	(gfc_interface_sym_mapping, gfc_interface_mapping): New structures.
	(gfc_init_interface_mapping, gfc_free_interface_mapping)
	(gfc_get_interface_mapping_charlen, gfc_get_interface_mapping_array)
	(gfc_set_interface_mapping_bounds, gfc_add_interface_mapping)
	(gfc_finish_interface_mapping, gfc_apply_interface_mapping_to_cons)
	(gfc_apply_interface_mapping_to_ref)
	(gfc_apply_interface_mapping_to_expr)
	(gfc_apply_interface_mapping): New functions.
	(gfc_conv_function_call): Evaluate the arguments before working
	out where the result should go.  Make the null pointer case provide
	the string length in parmse.string_length.  Cope with non-constant
	string lengths, using the above functions to evaluate such lengths.
	Use a temporary typespec; don't assign to sym->cl->backend_decl.
	Don't assign to se->string_length when returning a cached array
	descriptor.

From-SVN: r104040