Make the jeeps code somewhat less weird w.r.t. packet allocation and

Make the jeeps code somewhat less weird w.r.t. packet allocation and
deallocation, letting the life cycle of the objects take care of
zeroing buffers and releasing them.

This same stick should be shaken at other code in jeeps...

Tested:
  Reads and writes of waypoints on 60CSX on Mac USB with address sanitizer.

git-svn-id: http://gpsbabel.googlecode.com/svn/trunk@4731 f51c46e8-681c-474f-0cfe-069cfd0219fb