This function replaces xbps_repository_get_path_from_pkg_dict() and
xbps_get_binpkg_local_path(). It takes a pkg dictionary as returned
by a repository pkg index or a transaction dictionary and returns
a string with the full path to the binary pkg, either in local
repos, cachedir or remote repos.
Update all code to use this function... sorry I broke ABI compatiblity.