Add "Rust" to the ports tree

[macports.org@…]

​Rust 0.1 was officially released yesterday. Rust is an interesting take on the systems language: it goes for roughly the same niche as Go, but its designers have decided to make it both lower-level at run-time and safer (by increasing compile-time guarantees and checkability). ​Its website describes it as:

Rust is a curly-brace, block-structured expression language. It visually resembles the C language family, but differs significantly in syntactic and semantic details. Its design is oriented toward concerns of “programming in the large”, that is, of creating and maintaining boundaries – both abstract and operational – that preserve large-system integrity, availability and concurrency.

From the release mail,

• the 0.1 tarball can be found at: ​http://dl.rust-lang.org/dist/rust-0.1.tar.gz
• signature file: ​http://dl.rust-lang.org/dist/rust-0.1.tar.gz.asc
• SHA-256 hash: a1a234592168443b3bd6dce03378ee410393b07f8075c6a56e339638fdda8263

A ./configure; make was sufficient to build a working compiler on my 10.6 machine, although the build process fetches a stage0 compiler (the rust compiler is written in rust) on the internet, I do not know if that fits in the normal Macports practices. It also builds a full LLVM, maybe it could depend on the macports-provided LLVM instead (not sure which version is needed, it built a 3.1dev from today)