Implemented amb632 - lookup_sequence, also added set_controller (since it dealt with models).
Implemented set_pev_string, for setting with an already allocated string handle. Also added pev_serial, to get the entity serial number.
1) New hookable Engine func: GetInfoKeyBuffer
2) New GameDLL func that can be called via engfunc: GetInfoKeyBuffer
3) New native: copy_infokey_buffer that copies data out of the specified info key buffer
4) EngFunc_InfoKeyValue, EngFunc_SetKeyValue, and EngFunc_SetClientKeyValue have been reworked
so that they expect pointers to an info key buffer in order to work properly o_O
5) Added some error messages to get_tr
