Fixed classes with undefined constructor.

IterativeRobot and BinaryImage had no constructor
defined (and so would give linker errors).
Error just had an empty constructor defined,
so I switched to "=default".

Change-Id: Ia8efb4282928227878dfefeda58ccb8cf06aabb2

wpilibc/wpilibC++/include/Error.h

@@ -20,7 +20,7 @@ class Error {
  public:
   typedef int32_t Code;
 
-  Error();
+  Error() = default;
   void Clone(const Error& error);
   Code GetCode() const;
   std::string GetMessage() const;