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/INTEGER.h b/skeletons/INTEGER.h
index a8b1658..2754b4b 100644
--- a/skeletons/INTEGER.h
+++ b/skeletons/INTEGER.h
@@ -16,6 +16,7 @@
 typedef ASN__PRIMITIVE_TYPE_t INTEGER_t;
 
 extern asn_TYPE_descriptor_t asn_DEF_INTEGER;
+extern asn_TYPE_operation_t asn_OP_INTEGER;
 
 /* Map with <tag> to integer value association */
 typedef struct asn_INTEGER_enum_map_s {