Turns out Function can do the jobs of both CallbackReceiver and
FunctionReceiver, so I've removed the latter two.
Also, shift and reset should work with a combination of types, not
just a single type, so I've expanded their generic signatures.
I've been told by knowledgeable people that it is impossible to
implement composable continuations (AKA delimited continuations AKA
shift/reset) in terms of call-with-current-continuation. Since I
don't yet understand why that is, I figured it would help my
understanding to attempt it and see how it fails.
If the VM runs out of heap space and the "avian.heap.dump" system
property was specified at startup, the VM will write a heap dump to
the filename indicated by that property. This dump may be analyzed
using e.g. DumpStats.java.
This makes heap dumps more useful since these classes are now refered
to by name instead of number.
This commit also adds a couple of utilities for parsing heap dumps:
PrintDump and DumpStats.
