gnu: libyajl: Don't use unstable tarball.

* gnu/packages/web.scm (libyajl)[source]: Use GIT-FETCH and
GIT-FILE-NAME.

gnu/packages/web.scm

@@ -786,13 +786,14 @@ style API.")
     (name "libyajl")
     (version "2.1.0")
     (source (origin
-              (method url-fetch)
-              (uri (string-append "https://github.com/lloyd/yajl/"
-                                  "archive/" version ".tar.gz"))
-              (file-name (string-append name "-" version ".tar.gz"))
+              (method git-fetch)
+              (uri (git-reference
+                    (url "https://github.com/lloyd/yajl.git")
+                    (commit version)))
+              (file-name (git-file-name name version))
               (sha256
                (base32
-                "0nmcqpaiq4pv7dymyg3n3jsd57yhp5npxl26a1hzw3m3lmj37drz"))))
+                "00yj06drb6izcxfxfqlhimlrb089kka0w0x8k27pyzyiq7qzcvml"))))
     (build-system cmake-build-system)
     (arguments
      '(#:phases