Cleanup: match argument names for function & declarations

Match function and declaration names, picking names based on
consistency with related code & clarity.

Also changes for old conventions, missed in previous cleanups:

- name -> filepath
- tname -> newname
- maxlen -> maxncpy

source/blender/python/mathutils/mathutils_Vector.h

@@ -42,10 +42,10 @@ PyObject *Vector_CreatePyObject_wrap(float *vec,
  * Create a vector where the value is defined by registered callbacks,
  * see: #Mathutils_RegisterCallback
  */
-PyObject *Vector_CreatePyObject_cb(PyObject *user,
+PyObject *Vector_CreatePyObject_cb(PyObject *cb_user,
                                    int vec_num,
                                    unsigned char cb_type,
-                                   unsigned char subtype) ATTR_WARN_UNUSED_RESULT;
+                                   unsigned char cb_subtype) ATTR_WARN_UNUSED_RESULT;
 /**
  * \param vec: Initialized vector value to use in-place, allocated with #PyMem_Malloc
  */