Region parameterization inference does not play well with explicit self

[nikomatsakis]

Right now the compiler incorrectly infers that a trait like:

trait Foo {
    fn get_foo(&self) -> &self/int;
}

must be region parameterized. This leads to various errors, for example using the Map trait. This will be a non-issue once the new region syntax is complete, because region parameterization will be explicit, but it's causing issues now. I've got a patch I was going to push as part of a larger pull request but due to the fact that I'm having trouble landing that big patch I am breaking it up into bits, and hence opening a separate issue for this.