gitignore: patterns for perl versions

Works now until perl 5.99.x
hv_impl.t tests: restore STDERR

If -v was specified then output was not visible anymore after the
first quiet_stderr call.
yml_to_bbd: separate with space only if needed

The problem was just that emacs highlighting in the BBBike mode is
broken if the name field ends with a trailing space. So make sure no
trailing spaces are written anymore.
hv_impl.t test: better counting of leaked scalars

All Test::More operations are now moved outside the NoteSV/CheckSV
checkpoints, so any scalars created by Test::More/Test::Builder do not
disturb anymore.