libpacman: Rework list item removal.
libpacman: Now that some stuff is fixed bring back f_ptrlist* to fptrlist.h.
libpacman: Drop FREELISTPTR.
libpacman: Drop FREELISTPKGS.
libpacman: Drop FPtrListItem and use plain FListItem<void *> instead.
libpacman: Additional fixes to make FList<T> more similar to FPtrList.
libpacman: Make FPtrList a little bit more correct with return types.
libpacman: Add FPtrListItem::swap_data.