- xbps_handle::transd -> new member with transaction dictionary.
- xbps_transaction_prepare: returns an int.
- xbps_transaction_commit: doesn't need any arg now.
- xbps_repository_pool_sync: doesn't need any arg now.
- xbps_pkgdb_update: removed xbps_handle * arg.
- xbps_transaction_missingdeps_get: removed, missing_deps array is in
xbps_handle::transd("missing_deps") array object.