icu71: init at 71.1

https://github.com/unicode-org/icu/releases/tag/release-71-1

pkgs/development/libraries/icu/71.nix

@@ -0,0 +1,4 @@
+import ./base.nix {
+  version = "71.1";
+  sha256 = "sha256-Z6fm5R9h+vEwa2k1Mz4TssSKvY2m0vRs5q3KJLHiHr8=";
+}

pkgs/top-level/all-packages.nix

@@ -17801,6 +17801,11 @@ with pkgs;
   } // (lib.optionalAttrs (stdenv.hostPlatform.isi686 && stdenv.cc.isGNU) {
       stdenv = gcc6Stdenv; # with gcc-7: undefined reference to `__divmoddi4'
     }));
+  icu71 = callPackage ../development/libraries/icu/71.nix ({
+    nativeBuildRoot = buildPackages.icu71.override { buildRootOnly = true; };
+  } // (lib.optionalAttrs (stdenv.hostPlatform.isi686 && stdenv.cc.isGNU) {
+      stdenv = gcc6Stdenv; # with gcc-7: undefined reference to `__divmoddi4'
+    }));
 
   icu = icu70;