Change Platform::loadAudioResource signature to get a void* instead of char* to represent the memory buffer.

The data isn't a character stream, so void* makes more sense.

Reviewed by: Sergio Correia
Remove Platform::loadResource from API.

loadResource is used to load WebKit internal resources, and WebKit can
read those files by itself.

As side effect Nix::Data was removed as well.

Reviewed by: Luciano Wolf