Spectator camera improvements. Minor client crash fix.

Added new spectator commands and convars:

• cl_spec_cam_dist - The camera distance used in spectator mode only

• cl_spec_cam_increase_dist - A command which will increase the distance by a given default interval (25). This is bound to mouse wheel down (on your mouse's scroll wheel).

• cl_spec_cam_decrease_dist - A command which will decrease the distance by a given default interval (25). This is bound to mouse wheel up (on your mouse's scroll wheel).

• cl_spec_cam_change_interval - The interval at which the camera distance is increased and decreased

• cl_spec_cam_height - The camera height used in spectator mode only

• cl_specspeed - The speed of camera movement whilst in free roam (client-side equivalent of sv_specspeed)

Fixed a client crash bug which commonly occurred upon connecting to a server.