librustc: Fix `expr_use_visitor` (and, transitively, the borrow check)
with overloaded calls.

This enforces the mutability and borrow restrictions around overloaded
calls.

Closes #14774.

[breaking-change]
travis: Move from travis_wait to time-passes

It's looking like we're still timing out all over the place with travis_wait
because the entire `make -j4 rustc-stage1` command is taking too long. Instead,
achieve roughly the same idea by just having `-Z time-passes` printing
information. We shouldn't have a pass that takes longer than 10 minutes in
isolation.
auto merge of #15313 : pcwalton/rust/overloaded-call-expr-use, r=alexcrichton

with overloaded calls.

This enforces the mutability and borrow restrictions around overloaded
calls.

[breaking-change]

Closes #12223.

r? @alexcrichton
auto merge of #15323 : alexcrichton/rust/no-travis-wait, r=huonw

It's looking like we're still timing out all over the place with travis_wait
because the entire `make -j4 rustc-stage1` command is taking too long. Instead,
achieve roughly the same idea by just having `-Z time-passes` printing
information. We shouldn't have a pass that takes longer than 10 minutes in
isolation.
librustc: Have the kind checker check sub-bounds in trait casts.

This can break code that looked like:

    struct S<T> {
        val: T,
    }
    trait Gettable<T> {
        ...
    }
    impl<T: Copy> Gettable<T> for S<T> {
        ...
    }
    let t: Box<S<String>> = box S {
        val: "one".to_string(),
    };
    let a = t as Box<Gettable<String>>;
    //                        ^ note no `Copy` bound

Change this code to:

    impl<T> Gettable<T> for S<T> {
    //   ^ remove `Copy` bound
        ...
    }

Closes #14061.

[breaking-change]