Revert "Revert "Turn DropClientMsg into a SyncMessage because it will call back into the VM""

This reverts commit 31b057479b015322605161b6f41cfaf5371a7c37.
Small improvements to the /play[Sound|Music] commands
Revert "Stop using entityState_t.solid for transmitting bboxes over the"

This reverts commit 615c3c3c6e7aa6d6c71085015a48675b7e21ff4c.
Revert "Fix 615c3c3."

This reverts commit 1e1171bf0377e1a8522056d982824be6cb6dd410.
Remove stereo support
Remove r_HeatHazeFix that noone uses anyway
Remove light/entity/interaction occlusion culling

1) Never enabled
2) Was badly implemented as it caused a GPU sync
3) AFAIK not what engines should do nowadays
GLSL function declarations should be after the compile macros
Remove CVAR_ARCHIVE cgame variables
Load the map when playing a demo
Add support for the "colorGrade" world spawn key
Fixes #473
Figured out the difference between SERVERINFO and SYSTEMINFO
Remove some redundancy and reorder SV_DropClient
Remove arg of BotAllocateClient and introduce SV_IsBot
Remove unused declaration and vars
Fix a copy paste error
Fix download-pk3.sh for BSD md5sum
Fix last download-pk3.sh patch for  with a space
Remove SDL1 support
Fix UI lags