_write_real_fh without IO::AIO and AnyEvent::AIO stalls on Linux

[miyagawa]

AE::Handle's on_drain and push_read stuff doesn't work nice on Linux.

You can try enable Plack::Middleware::Static (or Plack::App::File) and access those static files without AIO (PLACK_NO_SENDFILE=1) on linux. Works fine on OS X etc.