Rolling

https://media.discordapp.net/attachments/629477786943356938/666855050513088571/SPOILER_srb20133.gif (this PR doesn't add the roll anywhere in-game. just adds the option for lua modders)

todo: netsync player->viewrollangle (not doing so isn't an option since this makes nights control rotate to match it, which would cause desyncs!) also todo: ogl support I guess

loosely based (as in a clean-room-style implementation) of varren's old view roll, with adaptions using software fov to fix the black borders