C++: Add upgrade and downgrade scripts

Author: jketema

cpp/downgrades/4f9fabab5124d49108782c081579f45a70571d74/mangled_name.ql

@@ -0,0 +1,11 @@
+class Declaration extends @declaration {
+  string toString() { none() }
+}
+
+class MangledName extends @mangledname {
+  string toString() { none() }
+}
+
+from Declaration d, MangledName n
+where mangled_name(d, n, _)
+select d, n