adjust the execution-token (ie. the CFA) to point
to the parameter field (ie. the PFA) of a word.
this is not a constant operation - most words have their
parameters at "1 CELLS +" but CREATE/DOES-words have the
parameters at "2 CELLS +" and ROM/USER words go indirect
with a rom'ed offset i.e. "CELL + @ UP +"
core ordinary primitive