Adds 'rustc fails to detect duplicate switch cases due to integer ove…

…rflow' ICE

Reference: rust-lang/rust#13727

src/13727.rs

@@ -0,0 +1,11 @@
+fn test(val: u8) {
+    match val {
+        256 => print!("0b1110\n"),
+        512 => print!("0b1111\n"),
+        _   => print!("fail\n"),
+    }
+}
+
+fn main() {
+    test(1);
+}