add a libapt-pkg recommends apt

For many usecases like the acquire system libapt-pkg actually needs
tools and config found in the apt package. apt tends to be installed
everywhere libapt-pkg appears usually anyhow, but just in case to nudge
users (and tools) in the right direction.

Note that this isn't and shouldn't be a hard depends as there are
usecases working perfectly without 'apt' and as this is such an esoteric
problem incurring the costs arising from a Depends-Breaks-loop isn't
deemd as worth it.

debian/control

@@ -44,6 +44,7 @@ Multi-Arch: same
 Pre-Depends: ${misc:Pre-Depends}
 Depends: ${shlibs:Depends}, ${misc:Depends}
 Breaks: apt (<< 1.1~exp4), libapt-inst1.5 (<< 0.9.9~)
+Recommends: apt (>= ${binary:Version})
 Section: libs
 Description: package management runtime library
  This library provides the common functionality for searching and