This makes glassmaking more challenging, as glass that is quenched
when not molded, or left wandering too long, will tend to quench to
crude glass, which is inferior.
This also prevents molten glass from wandering the countryside
forever from failed glassmaking attempts, and precludes keeping
molten glass in "captivity" as a crude infinite light source.
Seems like minetest doesn't behave very well on trying to spawn
more than 1 particlespawner during a single tick.
Work around this so smoke comes out correctly...
