gnu: ecl: Remove 16.1.3.

This package fails to build and has no users in Guix.

* gnu/packages/sagemath.scm (ecl-16): Remove variable.
* gnu/packages/patches/ecl-16-format-directive-limit.patch,
gnu/packages/patches/ecl-16-ignore-stderr-write-error.patch,
gnu/packages/patches/ecl-16-libffi.patch: Delete files.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.

gnu/packages/sagemath.scm

@@ -170,27 +170,6 @@ represented as strings.")
     (license license:public-domain)
     (home-page "https://github.com/miguelmarco/libhomfly")))
 
-;; Sage 9.1 doesn't build with ECL 20.  This won't be necessary once 9.2 is
-;; released.  See https://trac.sagemath.org/ticket/22191
-(define-public ecl-16
-  (package
-    (inherit ecl)
-    (version "16.1.3")
-    (source
-     (origin
-       (method url-fetch)
-       (uri (string-append
-             "https://common-lisp.net/project/ecl/static/files/release/ecl"
-             "-" version ".tgz"))
-       (sha256
-        (base32 "0m0j24w5d5a9dwwqyrg0d35c0nys16ijb4r0nyk87yp82v38b9bn"))
-       (patches (search-patches
-                  "ecl-16-libffi.patch"
-                  "ecl-16-ignore-stderr-write-error.patch"
-                  "ecl-16-format-directive-limit.patch"))))
-    ;; Current ECL uses LGPL 2.1+
-    (license license:lgpl2.0+)))
-
 (define-public pynac
   (package
     (name "pynac")