Use Coccinelle's "depends on" directive to exclude files from certain
transformations. This should make them a bit simpler and possibly
faster, since we don't have to shell out to Python.
Unfortunately, this works only for file/directory exclusions. For
function and other more complex exclusions we still need to use Python,
at least for now.
Also, completely drop the file exclusion for man/ in the xsprintf
transformation, since we filter out everything under man/ before we even
run Coccinelle (in run-coccinelle.sh).
Some transformations generate results we don't want to keep, so
let's disable such transformations for specific files.
Also, disable const-strlen.cocci everywhere, as the STRLEN macro has a
pretty limited scope, so the transformation generates false positives in
most cases.
With these additions, coccinelle finds everything fixed by the first
commit in PR #7695. In order not to needlessly conflict with that PR
this PR won't include those fixes, but only the coccinelle changes to
detect them automatically in the future.