Bug#115899: apt needs to be more verbose when errors occur parsing files

[Adam Heath <doogie@debian.org>]

package: apt
version: 0.5.4

Reading Package Lists... Error!
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/dpkg/status
E: The package lists or status file could not be parsed or opened.

I had messed up a dd command in vi, and there really was no Package: header.
dpkg, in this situation, gives a line number.  apt's error is very much less
than helpful.