Enable more warnings & treat warnings as errors on Windows.

Change-Id: I2bf0144aaa8b670ff00b8e8dfe36bd4d237b9a8a
Reviewed-on: https://boringssl-review.googlesource.com/3140
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/tool/transport_common.cc b/tool/transport_common.cc
index 0f48703..453ff5e 100644
--- a/tool/transport_common.cc
+++ b/tool/transport_common.cc
@@ -32,11 +32,12 @@
 #else
 #define NOMINMAX
 #include <io.h>
+#pragma warning(push, 3)
 #include <WinSock2.h>
 #include <WS2tcpip.h>
+#pragma warning(pop)
+
 typedef int ssize_t;
-#define read _read
-#define write _write
 #pragma comment(lib, "Ws2_32.lib")
 #endif