Revert "gnu: Remove guile-2.2.4."

This reverts commit b1ca13ffb8.

See new comments in the code.

Fixes: guix/guix#2149
Change-Id: Ic58872d2e3289a1f8fda8bc601bcfa007547f2a4

gnu/packages/guile.scm

@@ -334,6 +334,20 @@ without requiring the source code to be rewritten.")
             (variable "GUILE_LOAD_COMPILED_PATH")
             (files '("lib/guile/2.2/site-ccache")))))))
 
+(define-public guile-2.2.4
+  ;; This has no dependencies, but is used in (guix quirks).
+  ;; Do not remove!
+  (package
+    (inherit guile-2.2)
+   (version "2.2.4")
+   (source (origin
+             (inherit (package-source guile-2.2))
+             (uri (string-append "mirror://gnu/guile/guile-" version
+                                 ".tar.xz"))
+             (sha256
+              (base32
+               "07p3g0v2ba2vlfbfidqzlgbhnzdx46wh2rgc5gszq1mjyx5bks6r"))))))
+
 (define-public guile-3.0
   ;; This is the latest Guile stable version.
   (package