ReceiveReliabilityLayer: avoid impure calls resetting types

Allow disabling blocking of IPs on packet errors

closes #239

Session: reject pongs whose timestamps are negative

this is unavoidable due to having no unsigned type in PHP. getLong() can return negative values.

SendReliabilityLayer: make retransmit timeout less insane

this hardcoded timeout really needs to be replaced by a calculation based on RTT, but that's a job for another time.

SendReliabilityLayer: do not send reliable packets outside the client…

…'s reliable window

The client implements a window of 512 packets, outside of which packets will be dropped. Eventually, the server will resend them, but after a long delay.
To avoid this, we buffer packets whose reliable message indexes are too large for the current reliable window.
This significantly improves performance when transmitting large amounts of data.

Fixed ack receipts not working for split packets

Merge branch 'legacy/0.14' into stable

CS

Merge branch 'next-major' into stable

ExceptionTraceCleaner: fixed empty stack traces when xdebug is enable…

…d, but not in develop mode