A listening socket can be enabled with the sockopt
TCP_DEFER_ACCEPT. This informs the kernel to not call the user-land
accept() until real data has been written to the socket.
A new flag LEV_OPT_DEFERRED_ACCEPT has been introduced to
automatically set this option. Optionally
evutil_make_tcp_listen_socket_deferred() can be called manually.
(Tweaked slightly by nickm.)
This reverts commit fab50488fcb741884ccdfa7b83643eac3e5c9cbf.
The function was, on reflection, not important enough to break the feature
freeze, since it's trivial to build on your own.
This is stuff that it's easy to get wrong (as I noticed when writing
bench_http), and that takes up a fair amount of space (see http.c).
Also, it's something that we'll eventually want to abstract to use
IOCP, where available.
svn:r1272
