Fix #1000: Support Proxy Protocol v2 ?

[victorwon2001]

Fixes #1000

Implementation summary

Added inbound PROXY v2 coverage, fixed parsing before SNI routing, and documented v1/v2 plus AWS NLB usage.

Changes

docs/content/cfg/_index.md                |   2 +-
 docs/content/deploy/amazon-elb.md         |  12 +-
 docs/content/feature/_index.md            |   2 +-
 docs/content/feature/proxy-protocol.md    |  15 +-
 docs/content/quickstart/_index.md         |   2 +-
 docs/content/ref/proxy.addr.md            |   7 +-
 fabio.properties                          |   7 +-
 proxy/inetaf_tcpproxy_integration_test.go |  49 ++++++
 proxy/serve.go                            |  17 +-
 proxy/tcp/tcptest/dialer.go               |  70 ++++++--
 proxy/tcp_integration_test.go             | 269 ++++++++++++++++--------------
 11 files changed, 286 insertions(+), 166 deletions(-)

Testing

Yes. Relevant repository checks passed.

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