Android 2.3 browser's compatibility

Added fallback replacement for missing functions and properties in Android 2.3 built-in browser.

While the code was placed almost arbitrarily, this doesn't affect the behaviour in already-compatible browsers - it just adds the fallback functionality if it's missing.


Haven't tested if one could win - yet -, but you can play until you lose in Android 2.3.6's browser.

A live preview is available at http://mgarciaisaia.github.io/2048/