fix illegal typecast

fixes crash during intermission caused by activated and held grenade
Keep selected player in op menus, when other player (dis)connects

Until now, when in, for example, kick player menu there was selected
some player and (dis)connected other player with lower CN, then this
earlier selected player was moved to other item in menu, but number
of selected item didn't change, so other player was selected.
Test work - ignore player menu
Add custom description of demos

Custom description is displayed in "Watching demo" and "Play demo" menu.
Add AssaultCube's CodeBlocks project for Linux
Fix - don't allow dead body of player to climb on ladder
Show additional small vote result for hidevote < 2

It's visible below radar.
Commit sets also default value of hidevote to 1.
Don't show HUD reflection on water surface

For reflectclip > 1 player's HUD reflects on water surface.