debugger: remove 'repl' command from builtinLibs

* It was displaying useless warning

lib/_debugger.js

@@ -754,6 +754,9 @@ function Interface(stdin, stdout, args) {
   this.repl = new repl.REPLServer('debug> ', streams,
                                   this.controlEval.bind(this), false, true);
 
+  // Do not print useless warning
+  repl._builtinLibs.splice(repl._builtinLibs.indexOf('repl'), 1);
+
   // Kill child process when main process dies
   this.repl.on('exit', function() {
     process.exit(0);

lib/repl.js

@@ -69,7 +69,7 @@ module.paths = require('module')._nodeModulePaths(module.filename);
 // Can overridden with custom print functions, such as `probe` or `eyes.js`
 exports.writer = util.inspect;
 
-var builtinLibs = ['assert', 'buffer', 'child_process', 'cluster',
+exports._builtinLibs = ['assert', 'buffer', 'child_process', 'cluster',
   'crypto', 'dgram', 'dns', 'events', 'fs', 'http', 'https', 'net',
   'os', 'path', 'punycode', 'querystring', 'readline', 'repl',
   'string_decoder', 'tls', 'tty', 'url', 'util', 'vm', 'zlib'];
@@ -181,7 +181,7 @@ function REPLServer(prompt, stream, eval, useGlobal, ignoreUndefined) {
 
     // Check if a builtin module name was used and then include it
     // if there's no conflict.
-    if (~builtinLibs.indexOf(cmd)) {
+    if (exports._builtinLibs.indexOf(cmd) !== -1) {
       var lib = require(cmd);
       if (cmd in self.context && lib !== self.context[cmd]) {
         self.outputStream.write('A different "' + cmd +
@@ -456,7 +456,7 @@ REPLServer.prototype.complete = function(line, callback) {
     }
 
     if (!subdir) {
-      completionGroups.push(builtinLibs);
+      completionGroups.push(exports._builtinLibs);
     }
 
     completionGroupsLoaded();