Eliminate C variables unused since 4d0fbddde6c5dcb9 refactored HvFILL()

3 functions had C variables previously used to track whether the number of
hash chains have any entries. 4d0fbddde6c5dcb9 refactored the hash
implementation to calculated this on demand, instead of tracking changes to
it on hash updates. That change missed eliminating those variables, as
gcc prior to 4.6.0 didn't actually warn that they weren't used, because
(technically) they aren't unused - they are assigned to, but never read.

gcc (at least 4.3.2 and 4.6.0) generates identical object code with/without
this change, implying that its optimiser correctly eliminates the code.
Other optimisers may be similar, in which case there's no runtime saving from
this change.