Add contrib/iostream3 to BUILD.gn

Change-Id: I9e7fac79ac142b2f93e9c56480897ecd918134f2
diff --git a/BUILD.gn b/BUILD.gn
index 7d1fa38..ec8bb2e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -119,3 +119,15 @@
   configs -= [ "//build/config:symbol_visibility_hidden" ]
   public_configs = [ ":zlib_config" ]
 }
+
+source_set("zfstream") {
+  sources = [
+    "contrib/iostream3/zfstream.cc",
+    "contrib/iostream3/zfstream.h",
+  ]
+
+  deps = [
+    ":zlib",
+  ]
+  public_configs = [ ":zlib_config" ]
+}
diff --git a/contrib/iostream3/LICENSE b/contrib/iostream3/LICENSE
new file mode 100644
index 0000000..6cbc822
--- /dev/null
+++ b/contrib/iostream3/LICENSE
@@ -0,0 +1,10 @@
+The code is provided "as is", with the permission to use, copy, modify,
+distribute and sell it for any purpose without fee.
+
+Ludwig Schwardt
+<schwardt@sun.ac.za>
+
+DSP Lab
+Electrical & Electronic Engineering Department
+University of Stellenbosch
+South Africa