Blockland r1922

Changes:

• Blockheads Ruin Xmas game mode added. Gather presents and jump into the fire pit to destroy them. Build by Sumz & Hamburger, code by Zor. (Note: I tweaked and reformatted the code, so problems may not necessarily be his fault)

• Removed $Pref::Steam::DisableSteam, replaced with -nosteam command line option

• Improved error messages for authentication dns/connection failures

• Vehicle steering options moved from "advanced" to "controls"