DESTROY - release a co-routine fcv.

Usage:

B:
   destroy( fcv );

C:
   void destroy(void *fcv);

Where:

fcv: is the control vector to be released.

Description:

DESTROY gets rid of a co-routine by doing a RLSEVEC on the fcv and the associated stack. An attempt to pass control to a DESTROYed co-routine will not be detected, but will lead to disaster.