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/tests/check-length.c b/skeletons/tests/check-length.c
index aa73b2c..d09e581 100644
--- a/skeletons/tests/check-length.c
+++ b/skeletons/tests/check-length.c
@@ -74,8 +74,8 @@
 	}
 
 
-	asn_DEF_OCTET_STRING.free_struct(&asn_DEF_OCTET_STRING, os, 0);
-	asn_DEF_OCTET_STRING.free_struct(&asn_DEF_OCTET_STRING, nos, 0);
+	ASN_STRUCT_FREE(asn_DEF_OCTET_STRING, os);
+	ASN_STRUCT_FREE(asn_DEF_OCTET_STRING, nos);
 }
 
 int