gnu: libgcrypt: Make old version 1.5.3 public.

* gnu/packages/gnupg.scm (libgcrypt-1.5): New variable.
* gnu/packages/ssh.scm (libssh): Use libgcrypt-1.5 instead of defining it
    ad-hoc.

gnu/packages/gnupg.scm

@@ -91,6 +91,18 @@ algorithms, public key algorithms, large integer functions and random number
 generation.")
     (license lgpl2.0+)))
 
+(define-public libgcrypt-1.5
+  (package (inherit libgcrypt)
+    (version "1.5.3")
+    (source
+     (origin
+      (method url-fetch)
+      (uri (string-append "mirror://gnupg/libgcrypt/libgcrypt-"
+                          version ".tar.bz2"))
+      (sha256
+       (base32
+        "1lar8y3lh61zl5flljpz540d78g99h4d5idfwrfw8lm3gm737xdw"))))))
+
 (define-public libassuan
   (package
     (name "libassuan")

gnu/packages/ssh.scm

@@ -80,21 +80,10 @@
                                       lib))))
                  %standard-phases)))
     (inputs `(("zlib" ,zlib)
-              ("libgcrypt"
                ;; Link against an older gcrypt, because libssh tries to access
                ;; fields of 'gcry_thread_cbs' that are now private:
                ;; src/threads.c:72:26: error: 'struct gcry_thread_cbs' has no member named 'mutex_init'
-               ,(package (inherit libgcrypt)
-                         (version "1.5.3")
-                         (source
-                          (origin
-                            (method url-fetch)
-                            (uri (string-append
-                                  "mirror://gnupg/libgcrypt/libgcrypt-"
-                                  version ".tar.bz2"))
-                            (sha256
-                             (base32
-                              "1lar8y3lh61zl5flljpz540d78g99h4d5idfwrfw8lm3gm737xdw"))))))))
+              ("libgcrypt", libgcrypt-1.5)))
     (native-inputs `(("patchelf" ,patchelf)))
     (synopsis "SSH client library")
     (description