pass the conv to extract_fmap

so it doesn't use a hard-coded ORELSEC but gets passed the appropriate
one
don't clear the hypotheses of FLOOKUP theorems

but clear the hypotheses of the results of using those theorems.
this makes finite map extraction fast, but the rest much slower -
possibly not a good tradeoff for the initial bootstrap, but probably
good for the label removal. might need to parameterise whether to do
this.