[common] support for mouse input when available

[pvmm]

• a different cursor shape (and probably a sprite instead of a tile) that moves around the screen preferably in pixels units;
• opens a cell (MINE_INPUT_OPEN) with a click of the button 1;
• flags a cell (MINE_INPUT_FLAG) with a click of the button 2;
• open multiple blocks (MINE_INPUT_OPEN_BLOCK) with a click of buttons 1 and 2;
• restart game by clicking on the game over pop up or message;