"As long an iterator" => "As long as an iterator"
Fix #11421
auto merge of #11451 : kud1ing/rust/patch-1, r=cmr
auto merge of #11452 : derekchiang/rust/fix-11421, r=cmr

Closes #11421.  A pretty trivial fix.
Improve invalid operator assignment handling.
auto merge of #11449 : rcatolino/rust/assign-binop-handling, r=alexcrichton

So far the following code
```
struct Foo;

fn main() {
  let mut t = Foo;
  let ref b = Foo;
  a += *b;
}
```
errors with 
```
test.rs:15:3: 13:11 error: binary operation + cannot be applied to type `Foo`
test.rs:15   *a += *b;
```
Since assignment-operators are no longer expanded to ```left = left OP right``` but are independents operators it should be 
```
test.rs:15:3: 13:11 error: binary operation += cannot be applied to type `Foo`
test.rs:15   *a += *b;
```
to make it clear that implementing Add for Foo is not gonna work. (cf issues #11143, #11344)

Besides that, we also need to typecheck the rhs expression even if the operator has no implementation, or we end up with unknown types for the nodes of the rhs and an ICE later on while resolving types. (once again cf #11143 and #11344).

This probably would get fixed with #5992, but in the meantime it's a confusing error to stumble upon.
@pcwalton, you wrote the original code, what do you think?
(closes #11143 and #11344)
Removed obsolete 'e' prefix on ty_evec and ty_estr.
Removed free_glue from tydesc (the code is still generated, but inlined in drop_glue).
Use the right type for self in methods and remove obsoleted items.
Fixes #7411, #10615.