bugfix + minor mathutils.Vector edits.

- multiplying a 2D vector by a 3x3 or 4x4 matrix would use un-initialized memory, now throw an exception.
- use more variable length array BLI_math functions.

source/blender/python/generic/mathutils_vector.h

@@ -43,7 +43,7 @@ typedef struct {
 } VectorObject;
 
 /*prototypes*/
-PyObject *newVectorObject(float *vec, int size, int type, PyTypeObject *base_type);
+PyObject *newVectorObject(float *vec, const int size, const int type, PyTypeObject *base_type);
 PyObject *newVectorObject_cb(PyObject *user, int size, int callback_type, int subtype);
 
 #endif				/* MATHUTILS_VECTOR_H */