Signal sent from work_signal() may interrupt the low priority worker thread that is already running. For example, the worker thread that is waiting for a semaphore could be woken up by the signal and break any synchronization assumption as a result. It also does not make any sense to send signal if it is already running and busy. This commit fixes it.

Update TODO.  Provide do-nothing stubs for mutex attribute interfaces if features not enabled.  pthread_cond includes a signaling semaphore and should call sem_setprotocol.

configs/nucleo_f303re: Various fixes to get the adc configuration building again after PR.  Refresh all configurations.

sem_setprotocol: Handle a case of missing proxy for sem_setprotocol.  Reorder so that (1) this error is avoided, and (2) >No proxy is needed if priority inheritance is not enabled.

arch: Disable priority inheritance on all semaphores used for signaling in the rest of the MCU drivers

Back out the rest of commit 1e754402.  Newlib support will not be accepted into the NuttX repository.

Back out the rest of commit 1e754402.  Newlib support will not be accepted into the NuttX repository.

SAMV7: Fix to SPI-Master driver.  Without this the chip select decoding feature will not work properly

drivers/serial.c: Make sure that priority inheritance is not enabled for the signaling semaphores used in the serial driver.

Semaphores: Provide macros for sem_setprotobol() and sem_getprotocol() if priority inheritance is not enabled.  More SEM_PRIO_* definitions to include/nuttx/semaphore.h

Move protoypes for the non-standard include/semaphore.h file to the non-standard include/nuttx/semaphore.h with the other non-standard semaphore interfaces.