Add miniz library to third_party, use it on Windows

tests/PDFPrimitivesTest.cpp

Index: tests/PDFPrimitivesTest.cpp
diff --git a/tests/PDFPrimitivesTest.cpp b/tests/PDFPrimitivesTest.cpp
index b1d482ffa2d4ee662055d6cb427bfe0db6aa9c5f..7ec395f5fdf1606a478b130d3f084cff2b27a0ba 100644
--- a/tests/PDFPrimitivesTest.cpp
+++ b/tests/PDFPrimitivesTest.cpp
@@ -295,8 +295,7 @@ static void TestFlateDecode(skiatest::Reporter* reporter) {
               "/ColorSpace /DeviceRGB\n"
               "/BitsPerComponent 8\n"
               "/Filter /FlateDecode\n"
-              "/Length 13\n"
-              ">> stream",
+              "/Length ",
               false);
 }