Remove pmsyncpkg_t

Remove pmsyncpkg_t

pmsyncpkg_t data sructure was removed:
1. pmpkg_t.reason is used instead of pmsyncpkg_t.newreason. (The target
packages come from sync repos, so we can use this field without any
problems. Upgrade transaction also uses this field to store this info.)
2. pmsyncpkg_t.removes was moved to pmpkg_t.removes.
This step requires careful programming, because we don't duplicate packages
when we add them to trans->packages. So we modify sync pkgcache when we
add this transaction-only info to our package. Hence it is important to
free this list when we remove any package from the target list
(remove_unresolvable, remove_conflicts, trans_free), otherwise this could
confuse the new sync transactions (with non-pacman GUI).

Overall, our code became ~100 line shorter, and we can call our helper
functions directly on trans->packages in sync.c, we don't need to maintain
parallel package lists.

Signed-off-by: Nagy Gabor <ngaba@bibl.u-szeged.hu>
Signed-off-by: Dan McGee <dan@archlinux.org>