Bug 940707 - Get more accurate latency numbers when using OpenSL.  r=sotaro,kinetik

This dlopen libmedia.so, fetches some symbols and use that to determine the
output latency of the stream.

This also includes some fixes to get the minimal latency on Android 4.0.4, and
makes the latency a bit better.
Bug 944132 - Make sure we don't loose precision when computing the audio clock when using opensl. r=sotaro