Fixes a major bug with g_multijump, causing insane speeds when respawning and pressin...

Fixes a major bug with g_multijump, causing insane speeds when respawning and pressing jump + forward. Antilag takeback velocity compares origins to determine velocity over a given amount of time. And if this float isn't set, it compares the distance from where the player was and where he respawns, causing insane speeds. This is already set for teleporters, but this commit also adds it when respawning, since we are teleported to another origin.