Hazardly low pressure induces OxyLoss up to 55 points

Induces OxyLoss when being in hazardly low pressures of 20 kPa and below.

**Internals on:** 11 OxyLoss per 4 ticks
**Internals off:** 16 OxyLoss per 4 ticks

Pressure-induced OxyLoss will stop when hitting 55 points, slightly above the threshold it causes unconsciousness. We do not want to cause deaths much sooner, we simply want to incapacitate them.

Breathing (the only part of the life proc where OxyLoss was handled so far) and Pressure Environments being entirely different procs makes the OxyLoss value getting changed *twice* every *four* ticks, in case internals are *on*.
The way this is currently handled, though, didn't actually allow for better solutions. Input is welcome.

Low pressures causing unconsciousness was [voted](http://baystation12.net/forums/viewtopic.php?f=5&t=10654&hilit=unconsciousness+vote) upon by the community.