parser rejects "fail []"

[jruderman]

fn main() {
    fail [];
}

/Users/jruderman/Desktop/a.rs:2:9:2:10: error: expected ';' or '}' after expression but found [

The parser should accept this, leaving it for the type-checker to complain about. Found through AST fuzzing.

[catamorphism]

Happily, the fix for #676 fixes this too. Added the code example as a test case, thanks!