Remove using namespace std;

For historical reasons we had a "using namespace std;" in port.h. This
is generally a bad idea. So removing it and along the way doing a bunch
of cpplint cleanup.

Change-Id: Ia125601a55ae62695e247fb0250df4c6f86c46c6
diff --git a/internal/ceres/block_random_access_diagonal_matrix_test.cc b/internal/ceres/block_random_access_diagonal_matrix_test.cc
index aa2d664..9308861 100644
--- a/internal/ceres/block_random_access_diagonal_matrix_test.cc
+++ b/internal/ceres/block_random_access_diagonal_matrix_test.cc
@@ -43,7 +43,7 @@
 class BlockRandomAccessDiagonalMatrixTest : public ::testing::Test {
  public:
   void SetUp() {
-    vector<int> blocks;
+    std::vector<int> blocks;
     blocks.push_back(3);
     blocks.push_back(4);
     blocks.push_back(5);