Description

   This routine destroys the condition variable specified by cond.
   This effectively uninitializes the condition variable. Call this
   routine when a condition variable will no longer be referenced.
   Destroying a condition variable allows the Threads Library to
   reclaim internal memory associated with the condition variable.

   It is safe to destroy an initialized condition variable upon
   which no threads are currently blocked. Attempting to destroy a
   condition variable upon which other threads are blocked results
   in unpredictable behavior.

   The results of this routine are unpredictable if the condition
   variable specified in cond either does not exist or is not
   initialized.