Change dataiterator, repo_search, and repo_write so that it
uses only the value in the last repodata if multiple repodata
sections have an entry for the keyname.
We do this by first setting up a keyskip array that maps
keynames to a base + repodataid value. We skip a key
if the repodataid does not match the entry in the keyskip
array.
The base is used so that we do not have to clear the array
for the next search. Instead, the base is simply set to a
value greater than all the current entries.
WARNING: As this adds two new elements to the Dataiterator,
this is an INCOMPATIBLE ABI CHANGE. We'll use this to do
a couple of cleanup commits in the next days that have been
postponed until now. We'll bump the soname before doing the
next release.
241123391f