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/BMPString.h b/skeletons/BMPString.h
index a3c5ef6..198b9e5 100644
--- a/skeletons/BMPString.h
+++ b/skeletons/BMPString.h
@@ -14,6 +14,7 @@
 typedef OCTET_STRING_t BMPString_t;  /* Implemented via OCTET STRING */
 
 extern asn_TYPE_descriptor_t asn_DEF_BMPString;
+extern asn_TYPE_operation_t asn_OP_BMPString;
 extern asn_OCTET_STRING_specifics_t asn_SPC_BMPString_specs;
 
 asn_struct_print_f BMPString_print;	/* Human-readable output */