core: add ROUND_UP() macro

src/node_internals.h

@@ -42,6 +42,10 @@ namespace node {
 # define ARRAY_SIZE(a) (sizeof((a)) / sizeof((a)[0]))
 #endif
 
+#ifndef ROUND_UP
+# define ROUND_UP(a, b) ((a) % (b) ? ((a) + (b)) - ((a) % (b)) : (a))
+#endif
+
 // this would have been a template function were it not for the fact that g++
 // sometimes fails to resolve it...
 #define THROW_ERROR(fun)                                                      \