Add comment about 'new' to HACKING

HACKING

@@ -98,6 +98,17 @@ We try to be quite consistent, but of course, that's not always possible.
   The exceptions to this rule are for objects with __iterator__ set,
   and for XML objects (see README.E4X).
 
+* Avoid using 'new' with constructors where possible, and use [] and
+  {} rather than new Array/new Object.
+  Right:
+    RegExp("^" + foo + "$")
+    Function(code)
+    new Date
+  Wrong:
+    new RegExp("^" + foo + "$")
+    new Function(code)
+    Date() // Right if you want a string-representation of the date
+
 == Testing/Optimization ==
 
 TODO: Add some information here about testing/validation/etc.