Queue blood splats to avoid crash

When spawning blood splats, add them to a queue. Once the maximum has
been reached (BLOODSPLATQUEUESIZE = 512), remove the oldest blood splat
before adding a new one. Also, instead of crashing once MAXVISSPRITES is
reached, try to remove the oldest blood splat first. Failing that, exit
cleanly with with an error rather than crashing. MAXVISSPRITES has been
increased from 1024 to 2048.