add a crc field to aliashdr_t
model_alias.c:
set it for all models
cl_parse.c:
set the pmodel and emodel info keys to the crcs of the player and eye
models
r_local.h, r_shared.h, client.h and render.h at the same time (couldn't get
away from that:/) verly likely to be lots of breakage (eg, player and eye
models are NOT checksummed atm), but everything builds