1) This moves the service tid detection stuff from context to pt.
2) If LWS_MAX_SMP > 1, a default pthread tid detection callback is provided
on the dummy callback. Callback handlers that call through to the dummy
handler will inherit this. It provides an int truncation of the pthread
tid.
3) If there has been any service calls on the service threads, the pts now
know the low sizeof(int) bytes of their tid. When you ask for a client
connection to be created, it looks through the pts to see if the calling
thread is a pt service thread. If so, the new client is set to use the
same pt as the caller.
When a large deflate frame been received, WSAEnumNetworkEvents will indicate the socket is ready to read. And because the frame is compressed, it may not be consumed entirely(not all bytes ready to receive have been received), since WSAEnumNetworkEvents is edge triggered, and the socket read buffer never been drained, WSAEnumNetworkEvents will never indicate the socket is ready to read again. What here need is level trigger behavior, thus add additional recv with empty buffer to reset edge status.
