Fix end game window conflicting with ingame menu

Fixes #6311
Fix D2k infantry death sequences.
Fix wrong sequence lengths
Disconnected clients now listed as '(Gone)'.
Merge pull request #6371 from reaperrr/d2k-death-sequences

Fixed D2k infantry death sequences
Merge pull request #6335 from obrakmann/fix6311

Fix end game window conflicting with ingame menu
Merge pull request #6360 from huwpascoe/clientstatus

Player connection status report.
Improves tab completion in chat.

Pressing tab after completion now cycles to the next candidate.