might as well move all the pod tests to xt

diff --git a/t/pod.t b/xt/pod.t
similarity index 100%
rename from t/pod.t
rename to xt/pod.t

diff --git a/t/pod_coverage.t b/xt/pod_coverage.t
similarity index 100%
rename from t/pod_coverage.t
rename to xt/pod_coverage.t