* ext/socket/init.c (rsock_s_accept_nonblock): avoid parsing args
  [ruby-core:71439] [Feature #11339]
* ext/socket/rubysocket.h: adjust prototype
* ext/socket/socket.c (sock_accept_nonblock): make private
* ext/socket/tcpserver.c (tcp_accept_nonblock): ditto
* ext/socket/unixserver.c (unix_accept_nonblock): ditto
* ext/socket/lib/socket.rb (Socket#accept_nonblock):
  implement as wrapper, move RDoc
  (TCPServer#accept_nonblock): ditto
  (UNIXServer#accept_nonblock): ditto

target 0: a (ruby 2.3.0dev (2015-11-12 trunk 52550) [x86_64-linux])
target 1: b (ruby 2.3.0dev (2015-11-12 avoid-kwarg-capi 52550) [x86_64-linux]

-----------------------------------------------------------
accept_nonblock

require 'tempfile'
require 'socket'
require 'io/wait'
nr = 500000
Tempfile.create(%w(accept_nonblock .sock)) do |tmp|
  path = tmp.path
  File.unlink(path)
  s = UNIXServer.new(path)
  addr = Socket.sockaddr_un(path).freeze
  nr.times do
    s.accept_nonblock(exception: false)
    c = UNIXSocket.new(path)
    s.wait_readable
    s.accept_nonblock(exception: false).close
    c.close
  end
end

-----------------------------------------------------------
raw data:

[["accept_nonblock",
  [[4.807877402752638,
    4.930681671947241,
    4.738454818725586,
    4.69268161803484,
    4.684675686061382],
   [4.253904823213816,
    4.255124930292368,
    4.295955188572407,
    4.248479191213846,
    4.213303029537201]]]]

Elapsed time: 45.123040065 (sec)
-----------------------------------------------------------
benchmark results:
minimum results in each 5 measurements.
Execution time (sec)
name            a       b
accept_nonblock   4.685   4.213

Speedup ratio: compare with the result of `a' (greater is better)
name            b
accept_nonblock   1.112

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52601 b2dd03c8-39d4-4d8f-98ff-823fe69b080e