interlocked messagenumber
- lock on "select"
- empty "connected" check is possible now (no "no data read" exception or timeout)
- disabled client side socket.io ping (not threadsafe, must be improved first)
- better reconnect after connection failure/timeout
- more safer background read thread (no select on all handles at once: not threadsafe if other threads do a select too?)
shorter server loop (in case of "hanging" data?)
direct context as connection
Merge branch 'master' of https://github.com/andremussche/DelphiWebsockets