Improve the docs for curl_easy_pause

Several users seem to struggle with curl_easy_pause, I'd like to add a sentence to the docs, from where curl_easy_pause could be called to unpause a connection. I think, the progress callback is most suitable, because it should be called at least once per second even if idle or paused, right?
What do you think? Should make it much clearer, from where an unpause can be triggered, if calling from other threads is not possible.