nodejsUtils: additional Buffer safeguards for older Node.js

1. In allocBuffer(), ensure buffers allocated with new Buffer() are zero-filled.
   On newer Node.js versions, Buffer.alloc() zero-fills already.

2. In newBufferFrom(), throw when 'data' argument is a number.
   On newer Node.js versions, Buffer.from(number)/new Buffer(number, encooding)
   throw already.

lib/nodejsUtils.js

@@ -17,6 +17,11 @@ module.exports = {
         if (Buffer.from && Buffer.from !== Uint8Array.from) {
             return Buffer.from(data, encoding);
         } else {
+            if (typeof data === "number") {
+                // Safeguard for old Node.js versions. On newer versions,
+                // Buffer.from(number) / Buffer(number, encoding) already throw.
+                throw new Error("The \"data\" argument must not be a number");
+            }
             return new Buffer(data, encoding);
         }
     },
@@ -29,7 +34,9 @@ module.exports = {
         if (Buffer.alloc) {
             return Buffer.alloc(size);
         } else {
-            return new Buffer(size);
+            var buf = new Buffer(size);
+            buf.fill(0);
+            return buf;
         }
     },
     /**