Don't #define snprintf in VS2015 - it's illegal and unneeded.

VS 2015 supplies a conforming snprintf implementation, so #define
snprintf is no longer needed. Also, VS 2015 checks for #define of
snprintf and treats it as a fatal error.

LOG=Y
R=jarin@chromium.org
BUG=440500

Review URL: https://codereview.chromium.org/1078453002

Cr-Commit-Position: refs/heads/master@{#27690}

src/ostreams.cc

@@ -5,8 +5,10 @@
 #include "src/ostreams.h"
 
 #if V8_OS_WIN
+#if _MSC_VER < 1900
 #define snprintf sprintf_s
 #endif
+#endif
 
 namespace v8 {
 namespace internal {