Beginning of logic that will, hopefully, all me to build applications against a NuttX export package (vs. the nuttx/ source tree).

The ELF test/example has been extended so the individual ELF test programs can link against the SYSCALL library (if it is available) or against the C library to eliminate or minimize the need for symbol tables (2014-8-29).

STM32 FLASH fixes: use size_t instead of uint16_t, make interface more generic.  From Freddie Chopin

wdog.h does not contain any application interface, only internal OS interface.  Further, it is non-standard.  Move wdog.h from include/ to include/nuttx. For the same reason, move the description of the watchdog timer interfaces from the Users Guide to the Porting Guide.

Change the way PHY interrupts work: disable automatically.  Then we have to re-subscribe each time after the interrupt fires

NSH net monitor:  use a seamphore instead of boolean; use sem_timedwait instead of a boolean to communicate

Extend the NSH network initialization logic.  There is now an option that will create a network monitor thread that will monitor the state of the link.  When the link goes down, the code will attempt to gracefully put the Ethernet driver in a down state; When the link comes back, the code will attempt to bring the network back up.

More of the PHY event notification logic change:  Fix some compile errors when full feature is enabled; Add some missing ioctol logic

Change all time conversions.  Yech.  New timer units in microseconds breaks all existing logic that used milliseconds in the conversions.  Something likely got broken doing this, probably because I confused a MSEC2TICK conversion with a TICK2MSEC conversion.  Also, the tickless OS no appears fully functional and passes the OS test on the simulator with no errors

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.

Break reading and enqueueing of audio buffers into two steps so that errors in enqueueing can be distinguished for errors in reading.  Errors in enqueueing signal a downstream decoder error.  Add logic to gracefully recover from downstream decoder errors.

NxPlayer: Fix an error I introduced:  Need to pass through final buffer even if is it zero length because it contains the end of audio stream flag

Audio: Change how the end of the audio stream is detected by the leaf audio component.  This used by be done by looking for the first partial buffer.  That does not work with the in-place sub-sampling performed by the PCM decoder:  That always reduces the size of the buffer so that all buffers only partially filled by the time they get to the leaf.  Now, a flag is set in the audio buffer flags set to indicate the final buffer in the stream.