Important change to roots and other snares

Date:Thu Jun 28 19:02:40 2018
We fixed two bugs that have been making "drag back" snares (e.g. old forest
roots) silently release their victims for the past two years.

Bugs: Snares in rooms with random exits (e.g. old forest) would occasionally
release you if you spammed directions, and rooms containing multiple competing
snares would frequently forget about you after dragging you back once or twice.

What changed: Clumps of roots will once again keep you trapped until killed,
other snares will not release you either in the situations above. This will
make certain areas more difficult and re-enable some PK traps, so please be
extra careful if you relied on being able to just walk away!

What did not change: Some less common snares may offer a chance to escape,
and special features may set you free, but always with an explicit message.

As always, please use the "bug" command to report any cases we missed, or if
you think these fixes have introduced any unexpected side-effects. We want to
hear about it if you escape from a snare without a message.