Add some more libjingle targets to the GN build.

build/config/win/BUILD.gn

Index: build/config/win/BUILD.gn
diff --git a/build/config/win/BUILD.gn b/build/config/win/BUILD.gn
index d94dec389d78bde2e3349d285266f8365dbf46cb..0f00a1ee5b907de56be287bc301cdb94d453eca4 100644
--- a/build/config/win/BUILD.gn
+++ b/build/config/win/BUILD.gn
@@ -11,13 +11,11 @@ config("sdk") {
 
   defines = [
     "_ATL_NO_OPENGL",
-    "_WIN32_WINNT=0x0602",
     "_WINDOWS",
     "CERT_CHAIN_PARA_HAS_EXTRA_FIELDS",
     "NTDDI_VERSION=0x06020000",
     "PSAPI_VERSION=1",
     "WIN32",
-    "WINVER=0x0602",
   ]
 
   include_dirs = system_include_dirs
@@ -33,6 +31,15 @@ config("sdk") {
   }
 }
 
+# Sets the default Windows build version. This is separated because some
+# targets need to manually override it for their compiles.
+config("winver") {
+  defines = [
+    "_WIN32_WINNT=0x0602",
+    "WINVER=0x0602",
+  ]
+}
+
 # Linker flags for Windows SDK setup, this is applied only to EXEs and DLLs.
 config("sdk_link") {
   if (cpu_arch == "x64") {