Style: Set clang-format Standard to Cpp11

For us, it practically only changes the fact that `A<A<int>>` is now
used instead of the C++03 compatible `A<A<int> >`.

Note: clang-format 10+ changed the `Standard` arguments to fully
specified `c++11`, `c++14`, etc. versions, but we can't use `c++17`
now if we want to preserve compatibility with clang-format 8 and 9.
`Cpp11` is still supported as deprecated alias for `Latest`.

main/tests/test_physics.cpp

@@ -222,7 +222,7 @@ protected:
 
 	void make_grid(int p_width, int p_height, float p_cellsize, float p_cellheight, const Transform &p_xform = Transform()) {
 
-		Vector<Vector<float> > grid;
+		Vector<Vector<float>> grid;
 
 		grid.resize(p_width);