Remove automake subdir-objects; give libdmn/ its own Makefile.am

This is a partial backport of some work on the 2.x branches, so
that we can remove the subdir-objects option, as it seems to be
causing other problems on some platforms (Issue #69).
small dmn comment fixup
Merge branch 'master' into 2.x

Conflicts:
	gdnsd/libgdnsd/libdmn/Makefile.am
Merge branch '2.x' into systemd