I'm getting crashes and don't want to think about it. It may be time to
remove this, though it's needed for logging-storage to work from jni.
To be revisited....
I'm keeping it AND asserting at every possible location that the env
passed all the way in is the same as what the mapping produces. If in
months I haven't seen a single crash then I can evaluate which way of
passing the env around is better. (It'd be code size vs. performance,
as the passing of env is noticably faster. Code size could be fixed by
turning 'XWEnv xwe,' into a macro that goes away on some builds.)
So now all jni code uses a single dutil context, but also a single
mempool and jniutil instance instead of new instances of the latter two
per game and dict-iteration.
