Description

   This routine initializes the read-write lock attributes object
   referenced by attr and sets its attributes with default values.

   The results of calling this routine are undefined if attr
   references an already initialized read-write lock attributes
   object.

   After an initialized read-write lock attributes object has been
   used to initialize one or more read-write lock objects, any
   operation on that attributes object (including destruction) has
   no effect on those read-write lock objects.