Make this a proper C++ struct

This fixes a warning in Visual Studio 2019 ≥16.6 in C++14/17 mode (and error in C++ 20 mode)

Author: usiems

src/PythonQtClassWrapper.h

@@ -63,7 +63,7 @@ struct PythonQtDynamicClassInfo;
 //! a Python wrapper object for PythonQt wrapped classes
 //! which inherits from the Python type object to allow
 //! deriving of wrapped CPP classes from Python.
-typedef struct {
+struct PythonQtClassWrapper {
   PyHeapTypeObject _base;
 
   //! the additional class information that PythonQt stores for the CPP class
@@ -73,8 +73,7 @@ typedef struct {
   PythonQtClassInfo* classInfo() { return _classInfo; }
 
   PythonQtDynamicClassInfo* _dynamicClassInfo;
-
-} PythonQtClassWrapper;
+};
 
 //---------------------------------------------------------------