The steps when loading a savegame are:
1. The server loads the map.
2. Loading the map spawns all entities, i.e. their spawn func is called.
This loads the models, precaches the sounds, etc.
3. The savegame is loaded and all the entities in the edict are replaced
by the entities read from game.ssv.
When the monster footstep sound were added in cfb86ac, new sounds were
added to the spawn functions of most monster entities. This alters the
sound indices of all sounds precached at a later time. When a savegame
from an older version is loaded, the entities read from game.svv still
reference the old sound indices. This leads to the wrong sound getting
played.
Work around this by lazy loading the footstep sounds. Instead of loading
(precaching) them in the spawn function, load them at their first use.
This has the nice side effect of preventing the "missing sound" messages
when running without the footsteps.pkz file in baseq2/. It might lead to
short stuttering when the sound is played for the first time, though.
Closes#917.
bd97725a3d