Mention when type parameter could be `Clone`

```
error[E0382]: use of moved value: `t`
  --> $DIR/use_of_moved_value_copy_suggestions.rs:7:9
   |
LL | fn duplicate_t<T>(t: T) -> (T, T) {
   |                   - move occurs because `t` has type `T`, which does not implement the `Copy` trait
...
LL |     (t, t)
   |      -  ^ value used here after move
   |      |
   |      value moved here
   |
help: if `T` implemented `Clone`, you could clone the value
  --> $DIR/use_of_moved_value_copy_suggestions.rs:4:16
   |
LL | fn duplicate_t<T>(t: T) -> (T, T) {
   |                ^ consider constraining this type parameter with `Clone`
...
LL |     (t, t)
   |      - you could clone this value
help: consider restricting type parameter `T`
   |
LL | fn duplicate_t<T: Copy>(t: T) -> (T, T) {
   |                 ++++++
```

The `help` is new. On ADTs, we also extend the output with span labels:

```
error[E0507]: cannot move out of static item `FOO`
  --> $DIR/issue-17718-static-move.rs:6:14
   |
LL |     let _a = FOO;
   |              ^^^ move occurs because `FOO` has type `Foo`, which does not implement the `Copy` trait
   |
note: if `Foo` implemented `Clone`, you could clone the value
  --> $DIR/issue-17718-static-move.rs:1:1
   |
LL | struct Foo;
   | ^^^^^^^^^^ consider implementing `Clone` for this type
...
LL |     let _a = FOO;
   |              --- you could clone this value
help: consider borrowing here
   |
LL |     let _a = &FOO;
   |              +
```

1 files changed, 6 insertions, 1 deletions

diff --git a/tests/ui/borrowck/move-error-snippets.stderr b/tests/ui/borrowck/move-error-snippets.stderr
index 40b64398aef..97d14051518 100644
--- a/tests/ui/borrowck/move-error-snippets.stderr
+++ b/tests/ui/borrowck/move-error-snippets.stderr
@@ -13,7 +13,12 @@ note: if `A` implemented `Clone`, you could clone the value
   --> $DIR/move-error-snippets.rs:9:1
    |
 LL | struct A;
-   | ^^^^^^^^
+   | ^^^^^^^^ consider implementing `Clone` for this type
+   |
+  ::: $DIR/move-error-snippets-ext.rs:5:17
+   |
+LL |         let a = $c;
+   |                 -- you could clone this value
    = note: this error originates in the macro `aaa` which comes from the expansion of the macro `sss` (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider borrowing here
    |