gnu: Add cl-pngload.

* gnu/packages/lisp-xyz.scm (sbcl-pngload, cl-pngload, ecl-pngload): New
  variables.

gnu/packages/lisp-xyz.scm

@@ -12643,3 +12643,43 @@ (define-public cl-zpb-exif
 
 (define-public ecl-zpb-exif
   (sbcl-package->ecl-package sbcl-zpb-exif))
+
+(define-public sbcl-pngload
+  (package
+    (name "sbcl-pngload")
+    (version "2.0.0")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/bufferswap/pngload")
+             (commit version)))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32 "1ix8dd0fxlf8xm0bszh1s7sx83hn0vqq8b8c9gkrd5m310w8mpvh"))))
+    (build-system asdf-build-system/sbcl)
+    (inputs
+     `(("3bz" ,sbcl-3bz)
+       ("alexandria" ,sbcl-alexandria)
+       ("cffi" ,sbcl-cffi)
+       ("mmap" ,sbcl-mmap)
+       ("parse-float" ,sbcl-parse-float)
+       ("static-vectors" ,sbcl-static-vectors)
+       ("swap-bytes" ,sbcl-swap-bytes)
+       ("zpb-exif" ,sbcl-zpb-exif)))
+    (arguments
+     ;; Test suite disabled because of a dependency cycle.
+     ;; pngload tests depend on opticl which depends on pngload.
+     '(#:tests? #f))
+    (home-page "https://github.com/bufferswap/pngload")
+    (synopsis "PNG image decoder for Common Lisp")
+    (description
+     "This is a Common Lisp library to load images in the PNG image format,
+both from files on disk, or streams in memory.")
+    (license license:expat)))
+
+(define-public cl-pngload
+  (sbcl-package->cl-source-package sbcl-pngload))
+
+(define-public ecl-pngload
+  (sbcl-package->ecl-package sbcl-pngload))