Remove basic income.
Fix bound check in SetReverb
Make CvarSystem use auto& to iterate over cvars

Also do some cosmetic changes (docs, ...)
Fix cvars not being reset properly when sv_cheats is set to 0
Allow use of constexpr (where supported) via a macro.

This partially reverts c06667c4828cb7623f46e3c45a971f447c1f9394 but with
adaptations.
Make OffMeshConnections::MAX_CON constexpr.
UpdateReverbSlot: check slot no. and ratio.
Don't trust the reported data chunk size in WAV files.

This is not a full fix. Checking against (length - offset) is needed.
Remove alien group healing.
Make light armour available from the start.
Merge remote-tracking branch 'origin/master' into gameplay/viech