Need testing...

Moved CanBeIntegerized to its own package.

Removed "Word" from TypeSizes and uniformly import from uvm.refimpl.

Lifted xxxEntity outside match.

Fixed a bug in MemorySupport.cmpXchgEntity

TODO: Implement the new IR builder.

That type is only in the particular bundle I used for testing. Now the
micro VM has an internal type of the C "char**" type in its prelude.

Still breaking things.

The C binding does not use 1.8-specific features or deprecated features.
But some machines may still not have Java 1.8 installed. So I made the
JNI version configurable through a macro, and defaults to 1.6.

Fixes issue #59