that-rule preprocessing proposal

This is assuming that "that_adj" and maybe "_that" will go away (discussed on #96).  Otherwise, if "that_adj" stays, that THAT-EXCL-1 and THAT-EXCL-2 is not needed.  If "_that" stays, we will need a separate rule for it.

Targeted at "object clause", "content clause", "complement clause", etc, etc, but not "adjective clause".  [Is there a general name for these??]