Fix possibly wrong use of strncpy_s

src/platform-win32.cc

Index: src/platform-win32.cc
===================================================================
--- src/platform-win32.cc	(revision 6378)
+++ src/platform-win32.cc	(working copy)
@@ -1474,7 +1474,7 @@
 
 
 void Thread::set_name(const char* name) {
-  strncpy_s(name_, name, sizeof(name_));
+  OS::StrNCpy(Vector<char>(name_, sizeof(name_)), name, strlen(name));
   name_[sizeof(name_) - 1] = '\0';
 }