PARSE: new keyword restrictions

As part of the w:parse update, we are removing a few obscure word referencing capabilities:

You cannot use a variable to hold get and set word actions:

a: first [b:]
parse "abc" [a "abc"]  << an error now

You cannot use a variable to hold parse commands:

copie: 'copy
parse "abc" [copie here "abc"] << an error now

Keywords cannot be used as variables:

parse "abc" [copy: "abc"] << an error now

Please tell us immediately if this is a problem for you or your code.