A filter needs formats.h iff it uses FILTER_QUERY_FUNC();
since lots of filters have been switched to use something
else than FILTER_QUERY_FUNC, they don't need it any more,
but removing this header has been forgotten.
This commit does this; files with formats.h inclusion went down
from 304 to 139 here (it were 449 before the preceding commit).

While just at it, also improve the other headers a bit.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>