There's no need to prop_dictionary_copy the returned dictionary to
later have to free it again, just return directly the dictionary and
avoid the free(3)s.
1- We can cache the result of the first xbps_pkgdb_init() when it fails
and avoid the malloc/free/access from it.
2- We cache the uname(2) result into a private var in xbps_handle and
use it in xbps_pkg_arch_match().
This improves performance by ~5% approx and it's close as it was before
introducing the repository index format 1.5.
- 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.
