Bug#293838: please add file overlap check to lintian

[Adam Heath <doogie@debian.org>]

Package: lintian
Version: 1.23.3

I had a file overlap(/usr/share/doc/xen/examples/xmexample[12]) between xen
and xen-docs, both produced by the same source, and both installable at the
same time.  This kind of error should be easier to detect.

You'd have to take into account conflicts, when seeing if 2 packages were
installable at the same time.

This feature could also be extended when checking the entire archive; however,
that might be too heavy-weight.