Add a StmtPrinter test for implicit and explicit conversion operator calls.

Put back a comment that I removed too aggressively.

llvm-svn: 202255
diff --git a/clang/unittests/AST/DeclPrinterTest.cpp b/clang/unittests/AST/DeclPrinterTest.cpp
index 381536d..c604fb1 100644
--- a/clang/unittests/AST/DeclPrinterTest.cpp
+++ b/clang/unittests/AST/DeclPrinterTest.cpp
@@ -519,6 +519,7 @@
     "};",
     constructorDecl(ofClass(hasName("A"))).bind("id"),
     "A<T...>(T &&ts...) : T(ts)..."));
+    // WRONG; Should be: "A(T&&... ts) : T(ts)..."
 }
 
 TEST(DeclPrinter, TestCXXDestructorDecl1) {