pthread: add more robustness characteristics

pthread: add more robustness characteristics

pthread_mutex_lock() and trylock() will now return EOWNERDEAD if the
mutex is locked by a thread that no longer exists. Add
pthread_mutex_consistent() to recover from this situation. All credits
should go to Gregory Nutt who wrote the original commit.

Change-Id: Ife6319f6806e37cfba57a04992505b754b1712d3
Signed-off-by: Gregory Nutt <gnutt@nuttx.org>
[Song: backported 363403fb from NuttX]
Signed-off-by: EunBong Song <eunb.song@samsung.com>