Merged SDL2 changes from bartbes/love-experiments/SDL2 into default.

- Added love.system module, including clipboard functions.

- Added custom hardware cursors (love.mouse.newCursor, love.mouse.setCursor.)

- Revamped love.joystick:
-- added Joystick objects and moved love.joystick functions which operated on individual joysticks to methods on the Joystick objects.
-- Added love.joystick.getJoystick and love.joystick.getJoystickCount.
-- Added events for when joysticks are connected and disconnected.
-- Added 'Gamepad' methods to Joystick objects: Joystick:isGamepad, Joystick:getGamepadAxis, and Joystick:isGamepadDown. They're a common abstraction for xbox controller-like joystick across operating systems.

- Added monitor choosing support and "fullscreen desktop" mode to love.window.

- Moved unicode text input events to their own callback function (love.textinput), removed the key repeat functions from love.keyboard and made the second argument of love.keypressed a boolean saying whether the keypress was a repeat.

- liblove now works with love.window and love.graphics in OS X

src/modules/mouse/Mouse.h

@@ -22,8 +22,10 @@
 #define LOVE_MOUSE_MOUSE_H
 
 // LOVE
+#include "Cursor.h"
 #include "common/Module.h"
 #include "common/StringMap.h"
+#include "image/ImageData.h"
 
 namespace love
 {
@@ -49,6 +51,14 @@ public:
 
 	virtual ~Mouse() {};
 
+	virtual Cursor *newCursor(love::image::ImageData *data, int hotx, int hoty) = 0;
+	virtual Cursor *newCursor(Cursor::SystemCursor cursortype) = 0;
+
+	virtual void setCursor(Cursor *cursor) = 0;
+	virtual void setCursor() = 0;
+
+	virtual Cursor *getCursor() const = 0;
+
 	virtual int getX() const = 0;
 	virtual int getY() const = 0;
 	virtual void getPosition(int &x, int &y) const = 0;