gnu: Add ghc-transformers-base.

* gnu/packages/haskell.scm (ghc-transformers-base): New variable.

gnu/packages/haskell.scm

@@ -917,6 +917,35 @@ the paper \"Splittable Pseudorandom Number Generators Using Cryptographic
 Hashing\" by Claessen, Pałka for details and the rationale of the design.")
     (license bsd-3)))
 
+(define-public ghc-transformers-base
+  (package
+    (name "ghc-transformers-base")
+    (version "0.4.4")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append
+             "http://hackage.haskell.org/package/transformers-base/transformers-base-"
+             version
+             ".tar.gz"))
+       (sha256
+        (base32
+         "11r3slgpgpra6zi2kjg3g60gvv17b1fh6qxipcpk8n86qx7lk8va"))))
+    (build-system haskell-build-system)
+    (propagated-inputs
+     `(("ghc-stm" ,ghc-stm)))
+    (inputs
+     `(("ghc-transformers-compat" ,ghc-transformers-compat)))
+    (home-page
+     "http://hackage.haskell.org/package/transformers-compat")
+    (synopsis
+     "Backported transformer library")
+    (description
+     "Backported versions of types that were added to transformers in
+transformers 0.3 and 0.4 for users who need strict transformers 0.2 or 0.3
+compatibility to run on old versions of the platform.")
+    (license bsd-3)))
+
 (define-public ghc-transformers-compat
   (package
     (name "ghc-transformers-compat")