s:section_search(): Partially fix same-line bug
Partial fix for the bug described in
56e23aa19874159ef6faa9a8f80359418bb34568. We can now move to the
previous section start and the next section end. The last bug with this
is that neither of those motions work with the `v:count`. For now they
always jump to the next or previous section regardless of the count.
The `count` variable name was changed to `cnt` because Vim complained
about `count` being a read-only variable. I'm guessing it's some kind of
reserved word.