Send SIGDEBUG to the thread being denied a suspension/sleep state due
to XNTRAPLB, if the atypical/abnormal detection feature is armed.
The new SIGDEBUG_LOCK_BREAK alert code matches this case in the
siginfo data conveyed by SIGDEBUG.

At this chance, the related TCB state and information flag names have
been updated to better reflect the semantics:

XNTRAPSW -> XNWARN (SIGDEBUG warning enabled for atypical/abnormal
conditions)

XNSWREP -> XNPIALERT (Priority inversion alert sent [via SIGDEBUG])