Bug#478930: lintian: More info

[Mathieu Parent <math.parent@gmail.com>]

Package: lintian
Version: 1.23.46
Followup-For: Bug #478930

What this code do:
- parse the copyright file by sections (header, files, license, notice)
- report not rfc2822 copyright file
- report any missing field
- report unknown field
- report duplicated field (within a section)
- report free text
- check if all files are described in the copyright file, by expanding
  patterns
- check that all patterns match something

TODO:
- adapt to spec, if it changes
- implement match order (currently not needed)
- check if file header correspond to the copyright file (copyright,
  license)
- enhance doc
- ...

Please give feedback.