* make it possible to fall back to other sources on fail in MediaChange events

* make it possible to fall back to other sources on fail in MediaChange events

Patches applied:

 * michael.vogt@ubuntu.com--2005/apt--cdrom-fallback--0--base-0
   tag of apt@packages.debian.org/apt--main--0--patch-110

 * michael.vogt@ubuntu.com--2005/apt--cdrom-fallback--0--patch-1
   * initial patch to make falling back from cdrom possible

 * michael.vogt@ubuntu.com--2005/apt--cdrom-fallback--0--patch-2
   * fix in methods/cdrom.cc: don't call Fail() but return false so that apt can fallback to a differencent source

 * michael.vogt@ubuntu.com--2005/apt--mvo--0--patch-56
   * merged from apt--cdrom-fallback--0