Add a typeName() method to each type for error printing purposes.

Test: compiles with mma
Change-Id: I1283c395440282fde1106ad47aa185bdeda75880
diff --git a/Interface.cpp b/Interface.cpp
index 52e9a98..36179e7 100644
--- a/Interface.cpp
+++ b/Interface.cpp
@@ -57,6 +57,10 @@
     mReservedMethods.push_back(createSyspropsChangedMethod());
 }
 
+std::string Interface::typeName() const {
+    return "interface " + localName();
+}
+
 Method *Interface::createSyspropsChangedMethod() const {
     return new Method("notifySyspropsChanged",
             new std::vector<TypedVar *>() /*args */,