My VSIZE is no longer legal, and apparently there's no workaround (no
way to safely figure the length of an array whose size is known at
compile time.) To avoid the risk of duplicating little constants, added
macros that define length in a way a new VSIZE can pick it up. Couldn't
make that work for struct field arrays, however, so there I'm using
constants.
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.
