gnu: gd: Add fix for gd2_read test.

* gnu/packages/patches/gd-fix-gd2-read-test.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gd.scm (gd)[source]: Add patch.

gnu/local.mk

@@ -514,6 +514,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-cross-environment-variables.patch	\
   %D%/packages/patches/gcc-libvtv-runpath.patch			\
   %D%/packages/patches/gcc-5.0-libvtv-runpath.patch		\
+  %D%/packages/patches/gd-fix-gd2-read-test.patch		\
   %D%/packages/patches/gd-fix-tests-on-i686.patch		\
   %D%/packages/patches/gegl-CVE-2012-4433.patch			\
   %D%/packages/patches/geoclue-config.patch			\

gnu/packages/gd.scm

@@ -50,7 +50,8 @@
              (sha256
               (base32
                "0g3xz8jpz1pl2zzmssglrpa9nxiaa7rmcmvgpbrjz8k9cyynqsvl"))
-             (patches (search-patches "gd-fix-tests-on-i686.patch"))))
+             (patches (search-patches "gd-fix-gd2-read-test.patch"
+                                      "gd-fix-tests-on-i686.patch"))))
     (build-system gnu-build-system)
     (native-inputs
      `(("pkg-config" ,pkg-config)))

gnu/packages/patches/gd-fix-gd2-read-test.patch

@@ -0,0 +1,14 @@
+Fix a 'maybe-uninitialized' warning (turned error)
+which occurs on non-Intel platforms.
+
+--- libgd-2.2.3/tests/gd2/gd2_read.c	2016-07-21 01:21:16.000000000 -0400
++++ libgd-2.2.3/tests/gd2/gd2_read.c	2016-07-29 15:52:03.806405312 -0400
+@@ -5,7 +5,7 @@
+ 
+ int main(int argc, char *argv[])
+ {
+-	int error, i = 0;
++	int error = 0, i = 0;
+ 	gdImagePtr im, exp;
+ 	FILE *fp;
+ 	char *path[] = {