mathutils: refactor instantiation

remove 'type' argument, very few mathutils objects are wrapped,
add new function for creating wrapped objects.

also fixes unlikely memory leak if the data-array can't be allocated.

source/blender/python/mathutils/mathutils_Euler.h

@@ -43,9 +43,18 @@ typedef struct {
  * blender (stored in blend_data). This is an either/or struct not both */
 
 /* prototypes */
-PyObject *Euler_CreatePyObject(float eul[3], const short order, int type, PyTypeObject *base_type);
-PyObject *Euler_CreatePyObject_cb(PyObject *cb_user, const short order,
-                                  unsigned char cb_type, unsigned char cb_subtype);
+PyObject *Euler_CreatePyObject(
+        const float eul[3], const short order,
+        PyTypeObject *base_type
+        ) ATTR_WARN_UNUSED_RESULT;
+PyObject *Euler_CreatePyObject_wrap(
+        float eul[3], const short order,
+        PyTypeObject *base_type
+        ) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL(1);
+PyObject *Euler_CreatePyObject_cb(
+        PyObject *cb_user, const short order,
+        unsigned char cb_type, unsigned char cb_subtype
+        ) ATTR_WARN_UNUSED_RESULT;
 
 short euler_order_from_string(const char *str, const char *error_prefix);