Release 2018.1

In particular I'd like to get the `--copyup` changes out for an rpm-ostree
release that will use them. But there are other good changes here, and let's
keep up a regular release train 🚄 in general.

Closes: #1413
Approved by: jlebon

src/libostree/libostree-released.sym

@@ -451,6 +451,9 @@ LIBOSTREE_2017.15 {
   ostree_break_hardlink;
 } LIBOSTREE_2017.14;
 
+LIBOSTREE_2018.1 {
+} LIBOSTREE_2017.15;
+
 /* NOTE: Only add more content here in release commits!  See the
  * comments at the top of this file.
  */