Core: removed post_accept_timeout. Keeping post_accept_timeout in ngx_listening_t is no longer needed since we've switched to 1 second timeout for deferred accept in 5541:fdb67cfc957d. Further, using it in HTTP code can result in client_header_timeout being used from an incorrect server block, notably if address-specific virtual servers are used along with a wildcard listening socket, or if we've switched to a different server block based on SNI in SSL handshake.