Potential loss of information from DirToByte()/ByteToDir() usage

[VReaperV]

Currently, there's a few places in the game where DirToByte() and ByteToDir() are used to change a vec3_t into an int, and then back. This in a lot of cases results in incorrect data since you can't really put 12 bytes of arbitrary data into 4 bytes. It seems to only be used for some visual effects, like the shotgun spread and acid tubes effects, but it can be misleading nevertheless.