experimental multitouch based smooth scrolling

high-resolution mouse wheels aren't supported in userland yet, so why
don't we fake a high resolution touchpad instead 😄

it's somewhat working, though it seems to crash on startup when
installed (among other weird bugs).

src/controller/controls/mod.rs

@@ -2,6 +2,7 @@ mod media;
 mod null;
 mod paddle;
 mod scroll;
+mod scroll_mt;
 mod volume;
 mod zoom;
 
@@ -9,5 +10,6 @@ pub use self::media::*;
 pub use self::null::*;
 pub use self::paddle::*;
 pub use self::scroll::*;
+pub use self::scroll_mt::*;
 pub use self::volume::*;
 pub use self::zoom::*;