Fix keyboard for native targets.

I've tested targets cpp/neko/flash on linux with 2 azerty keyboards, all keys defined in utils.Key.hx are working.

I've also tested on windows neko/flash, beside the fact that neko believed my keyboard was a qwerty (it's an azerty) all worked fine.

See issue https://github.com/HaxePunk/HaxePunk/issues/71

Needs to be tested with a qwerty keyboard, and if possibly another layout, to see if that's a universal fix or not.

HTML5: I've tested it on linux, to do '~', '{' and '}' I need to press the 'Alt Gr' key and it's not working, some keys like F10, F11 are used by the web browser and are not detected by the game, all others keys are working ok.

PS: On both numpad I have the enter key is detected as a normal enter, so I didn't add the special case for NUMPAD_ENTER.