Copy code from controllib.pl and dpkg-gettext.pl to proper modules

Copy code from controllib.pl and dpkg-gettext.pl to proper modules

When trying to use proper perl modules together with stuff like
controllib.pl, all kind of "interesting" scoping issues arise.
Code that is already converted to modules should not use these
"old-style" modules. Create Dpkg::Gettext as a near verbatim copy
of dpkg-gettext.pl and a Dpkg::ErrorHandling as a container for some
error reporting functions from controllib.pl that are used by Raphael's
modules.

Note that this (at least Dpkg::ErrorHandling) should be only an interim
solution until a proper API gets defined.