Implement audio capture API

Please visit the following url to run the test MIDlet:
`http://localhost:8000/index.html?jars=tests/tests.jar&midletClassName=org.mozilla.AudioRecorder`

you can set the pref `media.navigator.permission.disabled` to `true` to disable the permission prompt.
Yes, i think so, `!!` makes sure a boolean value is returned, otherwise if `Media.PlayerCahe[handler]` is undefined, we got `undefined`, or `Media.PlayerCache[handle].audioRecorder` is returned.