Description

   This routine deletes a thread-specific data key key previously
   returned by a call to the tis_key_create() routine. The data
   values associated with key need not be NULL at the time this
   routine is called. The application must free any application
   storage or perform any cleanup actions for data structures
   related to the deleted key or associated data. This cleanup can
   be done before or after this routine is called. If the cleanup
   is done after this routine is called, the application must have a
   private mechanism to access any and all thread-specific values,
   contexts, and so on.

   Attempting to use the thread-specific data key key after calling
   this routine results in unpredictable behavior.

   No destructor functions are invoked by this routine. Any
   destructor functions that may have been associated with key will
   no longer be called upon thread exit.

   This routine can be called from destructor functions.