Automatically re-generated configuration variable documentation when NuttX release tarballs are created

Useless TIOCSERGSTRUCT logic in most serial drivers is not compiled unless CONFIG_DEBUG and CONFIG_SERIAL_TIOCSERGSTRUCT are defined

Various Kconfig files still have references to CONFIG_ variables.  Some in harmless comments, some in config definionts which is not harmless.  All removed

Reviewed all task exit logic.  For pthread_exit() moved some logic higher in the exit sequence that could be required to block.  For lower level logic kicked off by _exit(), add logic to prevent blocking when the task is not in a healthy state.

Documentation now expects autogenerated configuration variable documenation at Documentation/NuttXConfigVariables.html