gnu: Add rust-tokio-openssl-0.6.

* gnu/packages/crates-io.scm (rust-tokio-openssl-0.6): New variable.
(rust-tokio-openssl-0.4): Inherit from above.

gnu/packages/crates-io.scm

@@ -42664,8 +42664,35 @@ streams.")
      "This package provides the event loop that drives Tokio I/O resources.")
     (license license:expat)))
 
+(define-public rust-tokio-openssl-0.6
+  (package
+    (name "rust-tokio-openssl")
+    (version "0.6.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "tokio-openssl" version))
+       (file-name (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32 "0khjqv8wap79ki7h0l91rs8j0b4ix097lb40b4s1x9sa19ffq6xc"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:skip-build? #t
+       #:cargo-inputs
+       (("rust-futures" ,rust-futures-0.3)
+        ("rust-openssl" ,rust-openssl-0.10)
+        ("rust-pin-project" ,rust-pin-project-1)
+        ("rust-tokio" ,rust-tokio-1))))
+    (home-page "https://github.com/alexcrichton/tokio-openssl")
+    (synopsis "SSL streams for Tokio backed by OpenSSL")
+    (description
+     "This package is an implementation of SSL streams for Tokio backed by
+OpenSSL.")
+    (license (list license:expat license:asl2.0))))
+
 (define-public rust-tokio-openssl-0.4
   (package
+    (inherit rust-tokio-openssl-0.6)
     (name "rust-tokio-openssl")
     (version "0.4.0")
     (source
@@ -42676,7 +42703,6 @@ streams.")
        (sha256
         (base32
          "15751d47984ncvllagz35ldl10ifr8555wixvsg6k3i0yk2hhjrw"))))
-    (build-system cargo-build-system)
     (arguments
      `(#:tests? #f                      ;require internet access
        #:cargo-inputs
@@ -42688,12 +42714,7 @@ streams.")
     (native-inputs
      `(("pkg-config" ,pkg-config)))
     (inputs
-     `(("openssl" ,openssl)))
-    (home-page "https://github.com/alexcrichton/tokio-openssl")
-    (synopsis "SSL streams for Tokio backed by OpenSSL")
-    (description "This package is an implementation of SSL streams for Tokio
-backed by OpenSSL.")
-    (license (list license:expat license:asl2.0))))
+     `(("openssl" ,openssl)))))
 
 (define-public rust-tokio-openssl-0.3
   (package