conffile moving idiocy

conffile moving idiocy

* dh_installmodules: Give files in /etc/modprobe.d a .conf
  syntax, as required by new module-init-tools.
* dh_installmodules: Add preinst and postinst code to handle
  cleanly renaming the modprobe.d files on upgrade.
* Two updates to conffile moving code from wiki:
  - Support case where the conffile name is a substring of another
    conffile's name.
  - Support case where dpkg-query says the file is obsolete.