[Libwebsockets] please document lws_callback_function return codes

[Andy Green]

On 8/31/21 6:27 PM, Per Bothner wrote:
> I had problems remembering the return values for the protocal
> callback functions, and I couldn't find it in the documentation.
> 
> Can I suggest adding a \return comment for lws_callback_function
> in lws-callbacks.h?

Almost all of them will say the same, return 0 if no problem else 
nonzero to close.  There are a very few exceptions and they should 
describe their return already.

What was the callback you were looking at?

-Andy