mrustc (Mutabah's Rust Compiler)

mrustc is a "simple" rust compiler written in C++ that is able to
bootstrap a "recent" rustc.

As mrustc's primary goal is bootstrapping rustc, and as such it
tends to assume that the code it's compiling is valid (and any
errors in the generated code are mrustc bugs). Code generation is
done by emitting a high-level assembly (currently very ugly C, but
LLVM/cretone/GIMPLE/... could work) and getting an external tool
(i.e. gcc) to do the heavy-lifting of optimising and machine code
generation.
