rusti seg faults on simple vector definition

on linux x86-64:

```
$ rusti
WARNING: The Rust REPL is experimental and may be
unstable. If you encounter problems, please use the
compiler instead. Type :help for help.
rusti> let v = ~[1,23];
Segmentation fault (core dumped)
$ rustc --version
rustc 0.8-pre (bb35e23 2013-08-30 21:40:32 -0700)
```
