Move type operations to another structure

Every type has free, print, check_constraints, ber_decoder, der_encoder,
xer_decoder, xer_encoder, uper_decoder, uper_encoder and outmost_tag
operations. We move them out to a separate structure asn_TYPE_operation_t.

Combined with previous logic simplification, these operations are based
on ASN.1 basic types, constructed types and string types. So we can
reduce the space occupied by asn_TYPE_descriptor_t variables.
diff --git a/skeletons/constr_TYPE.c b/skeletons/constr_TYPE.c
index 322f68c..7a135ce 100644
--- a/skeletons/constr_TYPE.c
+++ b/skeletons/constr_TYPE.c
@@ -26,7 +26,7 @@
 	if(type_descriptor->tags_count)
 		return type_descriptor->tags[0];
 
-	return type_descriptor->outmost_tag(type_descriptor, struct_ptr, 0, 0);
+	return type_descriptor->op->outmost_tag(type_descriptor, struct_ptr, 0, 0);
 }
 
 /*
@@ -41,7 +41,7 @@
 	}
 
 	/* Invoke type-specific printer */
-	if(td->print_struct(td, struct_ptr, 1, _print2fp, stream))
+	if(td->op->print_struct(td, struct_ptr, 1, _print2fp, stream))
 		return -1;
 
 	/* Terminate the output */