Bug#874597: debian-installer: switch to debhelper 10

[Cyril Brulebois <kibi@debian.org>]

Source: debian-installer
Severity: normal

We're still using debhelper 7, and we're seeing such lines during the build:
| dh_clean: Compatibility levels before 9 are deprecated (level 7 in use)
| dh_installdirs: Compatibility levels before 9 are deprecated (level 7 in use)

… so I guess it's time we update debhelper compat and check Standards-Version.
Any takers?

While I'm at it, other deprecation warnings show up:
| depmod: WARNING: Ignored deprecated option -q
| depmod: WARNING: Ignored deprecated option -q
| depmod: WARNING: Ignored deprecated option -q
| depmod: WARNING: Ignored deprecated option -q


KiBi.