icu: make 58.2 coexists with 59.1

pkgs/development/libraries/icu/58.nix

···
+args @ { stdenv, fetchurl, fetchpatch, fixDarwinDylibNames }:
+let
+  keywordFix = fetchurl {
+    url = "http://bugs.icu-project.org/trac/changeset/39484?format=diff";
+    name = "icu-changeset-39484.diff";
+    sha256 = "0hxhpgydalyxacaaxlmaddc1sjwh65rsnpmg0j414mnblq74vmm8";
+  };
+in
+import ./base.nix {
+  version = "58.2";
+  sha256 = "036shcb3f8bm1lynhlsb4kpjm9s9c2vdiir01vg216rs2l8482ib";
+  patches = [ keywordFix ];
+  patchFlags = "-p4";
+} args

pkgs/development/libraries/icu/59.nix

···
+import ./base.nix {
+  version = "59.1";
+  sha256 = "1zkmbg2932ggvpgjp8pys0cj6z8bw087y8858009shkrjfpzscki";
+}

pkgs/development/libraries/icu/default.nix pkgs/development/libraries/icu/base.nix

···
+{ version, sha256, patches ? [], patchFlags ? "" }:
 { stdenv, fetchurl, fetchpatch, fixDarwinDylibNames }:
 
 let
   pname = "icu4c";
-  version = "59.1";
 in
 stdenv.mkDerivation {
   name = pname + "-" + version;
···
   src = fetchurl {
     url = "http://download.icu-project.org/files/${pname}/${version}/${pname}-"
       + (stdenv.lib.replaceChars ["."] ["_"] version) + "-src.tgz";
-    sha256 = "1zkmbg2932ggvpgjp8pys0cj6z8bw087y8858009shkrjfpzscki";
+    inherit sha256;
   };
 
   outputs = [ "out" "dev" ];
···
     sourceRoot=''${sourceRoot}/source
     echo Source root reset to ''${sourceRoot}
   '';
+
+  inherit patchFlags patches;
 
   preConfigure = ''
     sed -i -e "s|/bin/sh|${stdenv.shell}|" configure

pkgs/top-level/all-packages.nix

···
 
   hyena = callPackage ../development/libraries/hyena { };
 
-  icu = callPackage ../development/libraries/icu { };
+  icu58 = callPackage ../development/libraries/icu/58.nix { };
+  icu59 = callPackage ../development/libraries/icu/59.nix { };
+
+  icu = icu59;
 
   id3lib = callPackage ../development/libraries/id3lib { };
 
···
       libpng = libpng_apng;
       python = python2;
       gnused = gnused_422;
+      icu = icu59;
     };
   });