18.09: let's call it "Jackrabbit"

I was mainly considering Jellyfish and Jaguar (and Jackrabbit).
Originally I was inclined for Jellyfish, but then I thought of the
release T-shirts someone makes and it didn't seem suitable...
Jaguar would keep the name referring to a car as well, but as a
not-too-old (Mac) OS version is codenamed that way, I didn't go for it.

nixos/doc/manual/release-notes/rl-1809.xml

@@ -4,7 +4,7 @@
          version="5.0"
          xml:id="sec-release-18.09">
 
-<title>Release 18.09 (“??”, 2018/09/??)</title>
+<title>Release 18.09 (“Jackrabbit”, 2018/09/??)</title>
 
 <section xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"

nixos/modules/misc/version.nix

@@ -86,7 +86,7 @@ in
       versionSuffix = mkIf (pathIsDirectory gitRepo) (mkDefault (".git." + gitCommitId));
 
       # Note: code names must only increase in alphabetical order.
-      codeName = "Impala";
+      codeName = "Jackrabbit";
     };
 
     # Generate /etc/os-release.  See