copy more of the underlying TCPv4

fixes #211
bump mirage dep in opam

-> should be mirrored in the packages repo
parameterize `Tls_mirage.Make` over a `FLOW`

and fixup the ensuing error mess
drop the mock `Make_flow`

which synthesized a non-working `TCPV4` anyway
drop the extra module-type file
renames; it's no longer "tcp" that's needed
fixup mirage example #1
semi-fix example 2
Merge pull request #213 from mirleft/mirage-smaller-interface

Mirage smaller interface