RFE: add pthread_mutexattr_{gs}etrobust, pthread_mutex_consistent

This bug is split from bug 3055, which requested "the functions
pthread_mutexattr_getrobust_np, pthread_mutexattr_setrobust_np,
pthread_mutex_consistent_np and preferably the non-_np versions, plus their
supporting constants." The _np versions were added for LSB 4.1, while the
three non-np version were found to be blocked because they came in wth a newer
glibc:

"The non-_np versions come from the newer POSIX spec which are not yet able to
require in LSB 4.1, they are GLIBC_2.12 symbols. There's also a
pthread_sigqueue added in GLBIC_2.11 if we're tracking new symbols, and
pthread_setname_np and pthread_getname_np in GLIBC_2.12"
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