treewide icu61+ fixes

It's exactly the same issue as in the parent commit.
/cc #60250 (2fe63c8).

pkgs/applications/video/aegisub/default.nix

@@ -48,6 +48,9 @@ stdenv.mkDerivation rec {
 
   hardeningDisable = [ "bindnow" "relro" ];
 
+  # compat with icu61+ https://github.com/unicode-org/icu/blob/release-64-2/icu4c/readme.html#L554
+  CXXFLAGS = [ "-DU_USING_ICU_NAMESPACE=1" ];
+
   # this is fixed upstream though not yet in an officially released version,
   # should be fine remove on next release (if one ever happens)
   NIX_LDFLAGS = [

pkgs/development/libraries/languagemachines/libfolia.nix

@@ -16,6 +16,9 @@ stdenv.mkDerivation {
   buildInputs = [ automake autoconf bzip2 libtool autoconf-archive libtar libxml2 icu languageMachines.ticcutils ];
   preConfigure = "sh bootstrap.sh";
 
+  # compat with icu61+ https://github.com/unicode-org/icu/blob/release-64-2/icu4c/readme.html#L554
+  CXXFLAGS = [ "-DU_USING_ICU_NAMESPACE=1" ];
+
   meta = with stdenv.lib; {
     description = "A C++ API for FoLiA documents; an XML-based linguistic annotation format.";
     homepage    = https://proycon.github.io/folia/;

pkgs/tools/filesystems/darling-dmg/default.nix

@@ -20,6 +20,9 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ cmake fuse openssl zlib bzip2 libxml2 icu ];
 
+  # compat with icu61+ https://github.com/unicode-org/icu/blob/release-64-2/icu4c/readme.html#L554
+  CXXFLAGS = [ "-DU_USING_ICU_NAMESPACE=1" ];
+
   meta = {
     homepage = http://www.darlinghq.org/;
     description = "Darling lets you open macOS dmgs on Linux";