bg_pmove.c handles the player movement from both the
server and client. The client uses the function from cg_predict.c, in
that it predicts where the client will be based on velocity and
direction faced.
The entry function is Pmove, which calls PmoveSingle a number of times,
depending on the speed of the client. PmoveSingle then calls a function
to actually move the client depending on the type of client.