Add a way to get shorter spans until char for pointing at defs

```rust
error[E0072]: recursive type `X` has infinite size
  --> file.rs:10:1
   |
10 | struct X {
   | ^^^^^^^^ recursive type has infinite size
   |
   = help: insert indirection (e.g., a `Box`, `Rc`, or `&`) at some point to make `X` representable
```

vs

```rust
error[E0072]: recursive type `X` has infinite size
  --> file.rs:10:1
   |
10 |   struct X {
   |  _^ starting here...
11 | |     x: X,
12 | | }
   | |_^ ...ending here: recursive type has infinite size
   |
   = help: insert indirection (e.g., a `Box`, `Rc`, or `&`) at some point to make `X` representable
```

src/test/ui/resolve/issue-3907-2.stderr

@@ -2,7 +2,7 @@ error[E0038]: the trait `issue_3907::Foo` cannot be made into an object
   --> $DIR/issue-3907-2.rs:20:1
    |
 20 | fn bar(_x: Foo) {}
-   | ^^^^^^^^^^^^^^^^^^ the trait `issue_3907::Foo` cannot be made into an object
+   | ^^^^^^^^^^^^^^^ the trait `issue_3907::Foo` cannot be made into an object
    |
    = note: method `bar` has no receiver
 

src/test/ui/span/E0072.rs

@@ -0,0 +1,17 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+struct ListNode {
+    head: u8,
+    tail: Option<ListNode>,
+}
+
+fn main() {
+}

src/test/ui/span/E0072.stderr

@@ -0,0 +1,10 @@
+error[E0072]: recursive type `ListNode` has infinite size
+  --> $DIR/E0072.rs:11:1
+   |
+11 | struct ListNode {
+   | ^^^^^^^^^^^^^^^ recursive type has infinite size
+   |
+   = help: insert indirection (e.g., a `Box`, `Rc`, or `&`) at some point to make `ListNode` representable
+
+error: aborting due to previous error
+

src/test/ui/span/multiline-span-E0072.rs

@@ -0,0 +1,20 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// It should just use the entire body instead of pointing at the next two lines
+struct
+ListNode
+{
+    head: u8,
+    tail: Option<ListNode>,
+}
+
+fn main() {
+}

src/test/ui/span/multiline-span-E0072.stderr

@@ -0,0 +1,16 @@
+error[E0072]: recursive type `ListNode` has infinite size
+  --> $DIR/multiline-span-E0072.rs:12:1
+   |
+12 |   struct
+   |  _^ starting here...
+13 | | ListNode
+14 | | {
+15 | |     head: u8,
+16 | |     tail: Option<ListNode>,
+17 | | }
+   | |_^ ...ending here: recursive type has infinite size
+   |
+   = help: insert indirection (e.g., a `Box`, `Rc`, or `&`) at some point to make `ListNode` representable
+
+error: aborting due to previous error
+