Fixes and tweaks for OpenSL

Been playing with a Nexus 10 board the last days and found that audio was stuttering, even with crazy high latencies. Figured out why, which can explain broken audio on a lot of devices, the wrong sampling rate was used ...

This checks the native sampling rate, which avoided the problem on Nexus (44.1kHz seems to be the norm, not 48kHz) ... There are also patches for configurable latency and 2k block sizes instead of 8k block sizes. This might work just fine now that resampling isn't being hit ...

Works just fine now with decent latency on Nexus without a hitch here now.