Close #1349 Delimit NODE_PATH with ; on Windows

doc/api/modules.markdown

@@ -235,7 +235,8 @@ in pseudocode of what require.resolve does:
 
 If the `NODE_PATH` environment variable is set to a colon-delimited list
 of absolute paths, then node will search those paths for modules if they
-are not found elsewhere.
+are not found elsewhere.  (Note: On Windows, `NODE_PATH` is delimited by
+semicolons instead of colons.)
 
 Additionally, node will search in the following locations:
 

lib/module.js

@@ -481,7 +481,8 @@ Module._initPaths = function() {
   }
 
   if (process.env['NODE_PATH']) {
-    paths = process.env['NODE_PATH'].split(':').concat(paths);
+    var splitter = process.platform === 'win32' ? ';' : ':';
+    paths = process.env['NODE_PATH'].split(splitter).concat(paths);
   }
 
   modulePaths = paths;