* BODY> ( pfa -- cfa )

trying to convert a pointer to the parameter-field (PFA) to point
then to the corresponding code-field (CFA) - note that this is not
necessarily the inverse of >BODY instead it is a fast implementation
assuming a VARIABLE thing had been used. Every use of "BODY>" is
warned in the logfile.
 implementation-specific simulation:
   : BODY> CELL - ;

header ordinary primitive