Remove std:: prefixes from C functions in webrtc/.

std::memcpy -> memcpy for instance. This change was motivated by a
compile report complaining that std::rand() was used instead of rand(),
probably with a stdlib.h include instead of cstdlib. Use of C functions
without the std:: prefix is a lot more common, so removing std:: to
address this.

BUG=
R=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9549004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5658 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/neteq4/neteq_unittest.cc

@@ -14,10 +14,10 @@
 
 #include "webrtc/modules/audio_coding/neteq4/interface/neteq.h"
 
+#include <math.h>
 #include <stdlib.h>
 #include <string.h>  // memset
 
-#include <cmath>
 #include <set>
 #include <string>
 #include <vector>