Make tidy aware of Rust multiline strings

As a result of tighter and more correct handling of character
literals, this now catches a few kinds of syntax involving lifetimes
that were previously missed, so those have been updated.

python/tidy/servo_tidy_tests/multiline_string.rs

@@ -0,0 +1,28 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+// This puts a "multi-line string
+// inside of a comment" and then subsequently has a hyphenated-phrase
+
+
+const FOO: &'static str = "Do not confuse 'apostrophes',
+    They can be 'lifetimes' or 'characters'";
+
+
+fn main() {
+    assert!(foo("test
+                 foo-bar"));
+
+    assert!(foo("test
+                 test2 \"
+                 foo-bar"));
+
+    assert!(foo("test
+                 test2 \
+                 foo-bar"));
+
+    println!("This is a multiline string with a URL, which kinda, \
+             sorta looks like a comment https://github.com/servo/servo/");
+}