It now takes a frame cursor ref instead of a stack ref.

Switched Scala version to 2.12.2, the most recent stable version.  It
will now require Java 1.8.

Fixed existing uses of deprecated features.

Removed the `uvm.clientsupport` package.  This package was intended to
help Mu clients build text-based Mu IR bundles.  However, we started
using the IR Builder API instead, and the `uvm.clientsupport` package
remained unused.  The same capability can be provided by the
`mu-tool-compiler` project
(https://gitlab.anu.edu.au/mu/mu-tool-compiler).  `uvm.clientsupport`
provided a non-SSA-to-ssa converter, which can be useful for clients.
If there are needs of resurrecting that feature, please checkout the
previous commit.

It should treat the string parameter as an iref to a 0-terminated
string.

This will fix the problem that some memory is reclaimed by the GC before
the intended end-of-life. Now many classes implement the AutoCloseable
interface and manage their resources in the C++ style.

Moved CanBeIntegerized to its own package.

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

Still breaking things.

Fixes issue #59

KeepAlive -> Keepalive
Watchpoint -> WatchPoint
Fp -> FP