fix demos with UM_RequestDiagnostic

update protos + add support for DEM_Recovery command

only do handleFrameParsed once

Merge pull request #563 from markus-wa/s2-perf-improvements

Source 2 performance improvements

Merge pull request #560 from markus-wa/fix-nil-player

Merge pull request #559 from markus-wa/bullet-and-chat

readme: acknowledgements update (#558)

Merge pull request #547 from markus-wa/fix-userid-2

fix: possible nil players in game events (again)

Merge pull request #544 from markus-wa/fix-userid

Merge pull request #543 from markus-wa/up-proto