Fix problem with functor<>() not casting to the proper type and add unit test for this case

unittests/functor_creation_test.cpp

@@ -0,0 +1,16 @@
+#include <chaiscript/utility/utility.hpp>
+
+int main()
+{
+
+  chaiscript::ChaiScript chai;
+
+  chai.eval("def func() { print(\"Hello World\"); } ");
+
+  boost::function<void ()> f = chai.functor<void ()>("func");
+
+  f();
+
+  return EXIT_SUCCESS;
+
+}