Enable the -Wundef warning for clang

webrtc/examples/objc/AppRTCMobile/third_party/SocketRocket/SRWebSocket.m

 //
 //   Copyright 2012 Square Inc.
 //
 //   Licensed under the Apache License, Version 2.0 (the "License");
 //   you may not use this file except in compliance with the License.
 //   You may obtain a copy of the License at
 //
 //       http://www.apache.org/licenses/LICENSE-2.0
 //
 //   Unless required by applicable law or agreed to in writing, software
@@ skipping 551 matching lines @@
     if (_secure) {
         NSMutableDictionary *SSLOptions = [[NSMutableDictionary alloc] init];
         
         [_outputStream setProperty:(__bridge id)kCFStreamSocketSecurityLevelNegotiatedSSL forKey:(__bridge id)kCFStreamPropertySocketSecurityLevel];
         
         // If we're using pinned certs, don't validate the certificate chain
         if ([_urlRequest SR_SSLPinnedCertificates].count) {
             [SSLOptions setValue:[NSNumber numberWithBool:NO] forKey:(__bridge id)kCFStreamSSLValidatesCertificateChain];
         }
         
-#if DEBUG
+#ifdef DEBUG
         [SSLOptions setValue:[NSNumber numberWithBool:NO] forKey:(__bridge id)kCFStreamSSLValidatesCertificateChain];
         NSLog(@"SocketRocket: In debug mode.  Allowing connection to any root cert");
 #endif
         
         [_outputStream setProperty:SSLOptions
                             forKey:(__bridge id)kCFStreamPropertySSLSettings];
     }
     
     _inputStream.delegate = self;
     _outputStream.delegate = self;
@@ skipping 1169 matching lines @@
     }
 }
 
 - (NSRunLoop *)runLoop;
 {
     dispatch_group_wait(_waitGroup, DISPATCH_TIME_FOREVER);
     return _runLoop;
 }
 
 @end