gnu: m4: Remove already-applied patch.

* gnu/packages/patches/m4-readlink-EINVAL.patch: Remove file.
* gnu-system.am (dist_patch_DATA): Remove it.
* gnu/packages/m4.scm (m4): Remove patch.

gnu-system.am

@@ -403,7 +403,6 @@ dist_patch_DATA =						\
   gnu/packages/patches/lm-sensors-hwmon-attrs.patch		\
   gnu/packages/patches/luit-posix.patch				\
   gnu/packages/patches/m4-gets-undeclared.patch			\
-  gnu/packages/patches/m4-readlink-EINVAL.patch			\
   gnu/packages/patches/make-impure-dirs.patch			\
   gnu/packages/patches/mc-fix-ncurses-build.patch		\
   gnu/packages/patches/mcron-install.patch			\

gnu/packages/m4.scm

@@ -33,8 +33,7 @@
                                 version ".tar.bz2"))
             (sha256
              (base32
-              "0w0da1chh12mczxa5lnwzjk9czi3dq6gnnndbpa6w4rj76b1yklf"))
-            (patches (list (search-patch "m4-readlink-EINVAL.patch")))))
+              "0w0da1chh12mczxa5lnwzjk9czi3dq6gnnndbpa6w4rj76b1yklf"))))
    (build-system gnu-build-system)
    (arguments
     ;; XXX: Disable tests on those platforms with know issues.

gnu/packages/patches/m4-readlink-EINVAL.patch

@@ -1,18 +0,0 @@
-Newer Linux kernels would return EINVAL instead of ENOENT.
-The patch below, taken from Gnulib, allows the test to pass when
-these Linux versions are in use:
-https://lists.gnu.org/archive/html/bug-gnulib/2011-03/msg00308.html .
-
-diff --git a/tests/test-readlink.h b/tests/test-readlink.h
-index 08d5662..7247fc4 100644
---- a/tests/test-readlink.h
-+++ b/tests/test-readlink.h
-@@ -38,7 +38,7 @@ test_readlink (ssize_t (*func) (char const *, char *, size_t), bool print)
-   ASSERT (errno == ENOENT);
-   errno = 0;
-   ASSERT (func ("", buf, sizeof buf) == -1);
--  ASSERT (errno == ENOENT);
-+  ASSERT (errno == ENOENT || errno == EINVAL);
-   errno = 0;
-   ASSERT (func (".", buf, sizeof buf) == -1);
-   ASSERT (errno == EINVAL);