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

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/9559004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5657 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/talk/base/virtualsocket_unittest.cc b/talk/base/virtualsocket_unittest.cc
index 8188e1d..58dab14 100644
--- a/talk/base/virtualsocket_unittest.cc
+++ b/talk/base/virtualsocket_unittest.cc
@@ -25,11 +25,11 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <math.h>
 #include <time.h>
 #ifdef POSIX
 #include <netinet/in.h>
 #endif
-#include <cmath>
 
 #include "talk/base/logging.h"
 #include "talk/base/gunit.h"
@@ -686,7 +686,7 @@
     double num =
         receiver.samples * receiver.sum_sq - receiver.sum * receiver.sum;
     double den = receiver.samples * (receiver.samples - 1);
-    const double sample_stddev = std::sqrt(num / den);
+    const double sample_stddev = sqrt(num / den);
     LOG(LS_VERBOSE) << "mean=" << sample_mean << " stddev=" << sample_stddev;
 
     EXPECT_LE(500u, receiver.samples);
@@ -1002,7 +1002,7 @@
           double dev = (*f)[i].second - mean;
           sum_sq_dev += dev * dev;
         }
-        const double stddev = std::sqrt(sum_sq_dev / f->size());
+        const double stddev = sqrt(sum_sq_dev / f->size());
         EXPECT_NEAR(kTestMean[midx], mean, 0.1 * kTestMean[midx])
           << "M=" << kTestMean[midx]
           << " SD=" << kStdDev