Restore the apt ABI.

Restore the apt ABI.
The problem was that the size of pkgDpkgPM and its member offsets
changed because a map giving the names of the trigger states was
inserted into the middle of the structure.  I fixed it by using a
statically allocated array instead.  This changes the procedure for
looking up a string to a linear search, which should be fine (or
even faster than before) since there are only 4 state strings.  If
it becomes a problem, sorting the array by key will allow us to use
std::equal_range(), but I would advise against this unless it's
really necessary, since sooner or later someone will forget to maintain
the sort order.