Update Ubuntu (especially for recent CVEs)

- `ubuntu:artful`: 20170601
- `ubuntu:trusty`: 20170602
- `ubuntu:xenial`: 20170517.1
- `ubuntu:yakkety`: 20170517.1
- `ubuntu:zesty`: 20170517.1

library/ubuntu

@@ -8,34 +8,34 @@ GitFetch: refs/heads/dist
 # see also https://wiki.ubuntu.com/Releases#Current
 
 # commits: (master..dist)
-#  - fb06b03 Update tarballs
-#    - `ubuntu:artful`: 20170511.1
-#    - `ubuntu:trusty`: 20170330
-#    - `ubuntu:xenial`: 20170510
-#    - `ubuntu:yakkety`: 20170327
-#    - `ubuntu:zesty`: 20170411
-
-# 20170511.1
-Tags: 17.10, artful-20170511.1, artful, devel
-GitCommit: fb06b03251856d9a3c143332398512b3895e33b6
+#  - 784da92 Update tarballs
+#    - `ubuntu:artful`: 20170601
+#    - `ubuntu:trusty`: 20170602
+#    - `ubuntu:xenial`: 20170517.1
+#    - `ubuntu:yakkety`: 20170517.1
+#    - `ubuntu:zesty`: 20170517.1
+
+# 20170601
+Tags: 17.10, artful-20170601, artful, devel
+GitCommit: 784da92cdc6ac5fc1c42e69f878f02d2b012f7b4
 Directory: artful
 
-# 20170330
-Tags: 14.04.5, 14.04, trusty-20170330, trusty
-GitCommit: fb06b03251856d9a3c143332398512b3895e33b6
+# 20170602
+Tags: 14.04.5, 14.04, trusty-20170602, trusty
+GitCommit: 784da92cdc6ac5fc1c42e69f878f02d2b012f7b4
 Directory: trusty
 
-# 20170510
-Tags: 16.04, xenial-20170510, xenial, latest
-GitCommit: fb06b03251856d9a3c143332398512b3895e33b6
+# 20170517.1
+Tags: 16.04, xenial-20170517.1, xenial, latest
+GitCommit: 784da92cdc6ac5fc1c42e69f878f02d2b012f7b4
 Directory: xenial
 
-# 20170327
-Tags: 16.10, yakkety-20170327, yakkety
-GitCommit: fb06b03251856d9a3c143332398512b3895e33b6
+# 20170517.1
+Tags: 16.10, yakkety-20170517.1, yakkety
+GitCommit: 784da92cdc6ac5fc1c42e69f878f02d2b012f7b4
 Directory: yakkety
 
-# 20170411
-Tags: 17.04, zesty-20170411, zesty, rolling
-GitCommit: fb06b03251856d9a3c143332398512b3895e33b6
+# 20170517.1
+Tags: 17.04, zesty-20170517.1, zesty, rolling
+GitCommit: 784da92cdc6ac5fc1c42e69f878f02d2b012f7b4
 Directory: zesty