Commit 8704dde8 mistakenly removed this part of code -- it is not dead,
it is just that it will only fire when the user answered No at some of
the replacement prompts.  So... when we've rereached the starting line,
a found occurrence is invalid when it is beyond the starting x (either
after or before it, dependending on the direction of search).

This fixes https://savannah.gnu.org/bugs/?47816.