Bug#1082838: DebFile: Have to parse source field to extract source version

[Stefano Rivera]

Package: python3-debian
Version: 0.1.49
Severity: normal

DebFile.control.debcontrol() returns a bare Deb822 object representing
the CONTROL file. For a binnmu, this may contain:
Source: foo (1.0-1)

For Packages files we have the helper .source and .source_version
attributes to pares this for us.

Maybe .debcontrol() should return a Packages object with these helpers?

Stefano