Mark LINC-OE related parts, refactor, removed commented code

Marks are adder so that pure OF 1.3.2 can be more easily distinguished from
optical extension (LINC-OE) additions.
Remove unused ofp records and its decoding/encoding

The following records are affected:
- ofp_experimenter_multipart_header
- ofp_header
- ofp_multipart_request
- ofp_multipart_reply
- ofp_action_experimenter_header
Remove unused exports from ofp_v4_decode
Remove unused constant for experimenter header size