Fix Vector ConstIterator constructor.

The constructor was expecting a mutable pointer, while the passed pointer was
immutable (returns a const pointer), so the compilation was failing when iterating a constant.

core/templates/vector.h

@@ -229,7 +229,7 @@ public:
 		_FORCE_INLINE_ bool operator==(const ConstIterator &b) const { return elem_ptr == b.elem_ptr; }
 		_FORCE_INLINE_ bool operator!=(const ConstIterator &b) const { return elem_ptr != b.elem_ptr; }
 
-		ConstIterator(T *p_ptr) { elem_ptr = p_ptr; }
+		ConstIterator(const T *p_ptr) { elem_ptr = p_ptr; }
 		ConstIterator() {}
 		ConstIterator(const ConstIterator &p_it) { elem_ptr = p_it.elem_ptr; }