Tidy up handling of unimplemented features. These are expected (if undesirable) sorts of error, we should handle better than "backtrace and exit 2".

Autoderef objects when passing them as implicit (indirect) arg upon vtbl-dispatch.  Add testcase and XFAIL it on LLVM.  Closes #112.

The call to rust_start was assuming that all rust main() functions have the
same signature, but the compiler doesn't actually canonicalize them.  So
instead just match the C signature of rust_start, and cast.

Added a message passing system based on lock free queues for inter-thread communication. Channels now buffer on the sending side, and no longer require blocking when sending. Lots of other refactoring and bug fixes.

Add a test for an obvious-seeming (but not actually legal) kind of cast attempted in issue #115, downgrade bug to an err in type.ml so you get a better message.

Fix over-optimistic resolution of self-methods within obj scopes. There is no such feature in the language at present. Add test to prevent regression. Closes #114.

what to do with, rather than silently omitting it from the output.

This isn't complete: it misses line numbers in certain kinds of block.  It's
also still tricky to use it on Darwin, where we need to call dsymutil while the
.o file is still around in order for gdb to find the debugging symbols.

llvm-config may be installed somewhere that's not on the path or in ocaml's
default lib directory, so allow users to override $CFG_LLVM_CONFIG with an
environment variable and look up lib and binary paths through calls to
llvm-config.

The call to rust_start was assuming that all rust main() functions have the
same signature, but the compiler doesn't actually canonicalize them.  So
instead just match the C signature of rust_start, and cast.

implicitly or explicitly.

Fix IL translation of pattern-alt to allow a value of mutable/constrained type to be the subject of a pattern-alt.