Add a test for #4028

Author: topecongiro

Diff for: tests/target/skip/skip-with-trailing-comma.rs

@@ -0,0 +1,10 @@
+#![rustfmt::skip]
+
+fn myfunc1()
+{
+    println!("hi");      // yes I want my comments here
+} // keep this comment here too
+
+fn myfunc2() {
+    println!("bye");        // i want it that way
+} // tell me why