Fix Android 2.2 compatibility

Android 2.2 (FroYo) doesn't support some of Arrays' functions, such as copyOf() and copyOfRange().

Version 2.3.0 worked properly on Android 2.2, but 2.3.1 broke things when it introduced the usage of Arrays.copyOf() and Arrays.copyOfRange(). I added a new class, ArraysCompat, which implements all variants of these methods. This way compatibility is ensured.

Also, I think it's OK to eventually break compatibility with Android 2.2, as it's not massively used anymore, but I don't think it should be done on a point release (ie. from 2.3.0 to 2.3.1). Maybe in 2.4? :-)