message: Remove unused MISSING_MSGHDR_MSGFLAGS
  This check is not needed and not used in the code.
diff: @@ -184,12 +184,6 @@ AC_DEFUN([AC_SWOOLE_CHECK_SOCKETS], [
  AC_CHECK_FUNCS([hstrerror socketpair if_nametoindex if_indextoname])
  AC_CHECK_HEADERS([netdb.h netinet/tcp.h sys/un.h sys/sockio.h])
  - AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
  -#include <sys/types.h>
  -#include <sys/socket.h>
  - ]], [[static struct msghdr tp; int n = (int) tp.msg_flags; return n]])],[],
  - [AC_DEFINE(MISSING_MSGHDR_MSGFLAGS, 1, [ ])]
  - )
  AC_DEFINE([HAVE_SOCKETS], 1, [ ])
  dnl Check for fied ss_family in sockaddr_storage (missing in AIX until 5.3)
  