Add test for issue #1366.

As the comments in the issue state: it appears to work now, so this test
should just stop any regressions.

The second example in the issue description will format to the first,
which is then a fixed-point.

tests/source/issue-1366.rs

@@ -0,0 +1,12 @@
+fn main() {
+    fn f() -> Option<i32> {
+        Some("fffffffsssssssssddddssssfffffddddff").map(|s| s).map(|s| s.to_string()).map(|res| {
+            match Some(res) {
+                Some(ref s) if s == "" => 41,
+                Some(_) => 42,
+                _ => 43,
+            }
+        })
+    }
+    println!("{:?}", f())
+}

tests/target/issue-1366.rs

@@ -0,0 +1,13 @@
+fn main() {
+    fn f() -> Option<i32> {
+        Some("fffffffsssssssssddddssssfffffddddff")
+            .map(|s| s)
+            .map(|s| s.to_string())
+            .map(|res| match Some(res) {
+                     Some(ref s) if s == "" => 41,
+                     Some(_) => 42,
+                     _ => 43,
+                 })
+    }
+    println!("{:?}", f())
+}