Make debris SOLID_NOT, fixes #154

In lower mines you can drop a rock onto a tank by using a lever.
This was broken, the rock exploded instead of dropping, because debris
is spawned and that debris was solid.
Now the debris is not solid anymore (like it was up to
b4d16ab6b3
"Some additions to last commit:") and it works again

src/game/g_misc.c

@@ -399,7 +399,7 @@ ThrowDebris(edict_t *self, char *modelname, float speed, vec3_t origin)
 	v[2] = 100 + 100 * crandom();
 	VectorMA(self->velocity, speed, v, chunk->velocity);
 	chunk->movetype = MOVETYPE_BOUNCE;
-	chunk->solid = SOLID_BBOX;
+	chunk->solid = SOLID_NOT;
 	chunk->avelocity[0] = random() * 600;
 	chunk->avelocity[1] = random() * 600;
 	chunk->avelocity[2] = random() * 600;