Merge pull request #1337 in SNORT/snort3 from stream_tcp_dup_no_more to master

Merge pull request #1337 in SNORT/snort3 from stream_tcp_dup_no_more to master

Squashed commit of the following:

commit a10f22c3f011ddf297f9170fed3054a4b52b7023
Author: davis mcpherson <davmcphe.cisco.com>
Date:   Wed Jul 25 10:33:48 2018 -0400

    stream_tcp: update tsn state when partial buffer flushed, do not duplicate

    stream_tcp: delete tsn&data after flush, use seglist_base_seq to track progress

    use orig_dsize instead of payload_size for overlap math

    stream_tcp: eliminate 'buffered' field for tcp segment node struct

    stream_tcp: improve tcp segment state variable names and usage during reassembley and overlap processing

    stream_tcp: some refactoring to improve symbol names and code readability