Add a new option CONFIG_SCHED_TICKLESS to enable the tickless OS.  This is a work in progress but should be relatively safe since the new features are only enabled by this option (Safer but not 100% safe since it does not protect from typos and other dumb errors).

Rename up_timerinit() to up_timer_initailize(); Add prototypes for candidate interfaces for the tickless OS; Don't build existing timer initialization logic if CONFIG_SCHED_TICKLESS is defined.

NSH networking: There is now a configuration option that will bring up the network on an separate thread.  Since the network bring-up is asynchronous, there are not serial console start-up delays due to the network negotiation time.

PCM decoder: Handle errors in the PCM WAV file in a way that the Nxplayer can recover gracefully: Send and Audio Complete message.

WM8904: Add reset logic to put the part back in its initial state after playing each WAV file.  Base samles per second on frame length, not bits-per-sample.  Use a different frame length for 8-bit and 16-bit data

WM8904: Correct calculation of bitrate (I am not sure why this is correct). LR clock divisor is now a constant 32-bits per frame. Conditioned out interrupt logic; it is not being used. Also added some FLL lock interrupt/poll logic (which was subsequently disabled).

WM8904 interface enable method now returns the previous interrupt state.  Correct ordering of some WM8904: Need to provide MCLK before initializing the WM8904, not after

WM8904:  Tried disabling the SYSCLK while updating the FLL.  Didn't help but is still probably a correct change

WM8904:  Various updates to get BCLK/LRCLK correct.  Acutally worse the parent, but I think is on the right track

PCM decoder: Correct the end of audio stream handling.  It was not being detected before so that logic was not examining the WAV header in the first buffer of the next audio file