Bug#505857: debian-watch-file-should-mangle-version doesn't detect dversionmangle=auto

[Bertrand Marc]

Version: 2.5.113

Hi,

Lintian also doesn't detect dversionmangle=auto in debian/watch and reports a 
warning for this (see [2]).

Thanks,
Bertrand

[2] https://salsa.debian.org/games-team/7kaa/blob/master/debian/watch