Glog: Restore some custom config for MSVC2015

extern/glog/src/windows/config.h

@@ -1,5 +1,8 @@
 /* src/config.h.in.  Generated from configure.ac by autoheader.  */
 
+/* define if you have google gflags library */
+#define HAVE_LIB_GFLAGS 1
+
 /* Namespace for Google classes */
 #define GOOGLE_NAMESPACE google
 
@@ -9,6 +12,10 @@
 /* Puts following code inside the Google namespace */
 #define _START_GOOGLE_NAMESPACE_ namespace google {
 
+#if defined(__MINGW32__) || (defined(_MSC_VER) && (_MSC_VER >= 1900))
+#  define HAVE_SNPRINTF
+#endif
+
 /* Always the empty-string on non-windows systems. On windows, should be
    "__declspec(dllexport)". This way, when we compile the dll, we export our
    functions/classes. It's safe to define this here because config.h is only