fixed some packaging issues for 6L38

This fixes a bunch of little nits: removes GNUMake dependencies from Makefile.ams, removes some other Makefile.am warnings by setting subdir-objects, sets DEB_BUILD_MAINT_OPTIONS to hardening=-format to suppress some more warnings. Hope it helps.

Thanks huge for gnome-inform7.
This didn't work for me because the `\<` operator doesn't consider the slashes to be parts of words, and the double quotes make gtester think the expression is a name of a test binary. This one did work for me, however:
```sh
`echo $(SKIP_PATHS) | sed 's,\(^\|\s\+\)/, -s=/,g'`
```