Remove all using directives for STL namespace and members

Made all STL usages explicit to be able automatically find all usages of
particular class or function.

modules/features2d/test/test_brisk.cpp

@@ -42,6 +42,7 @@
 
 #include "test_precomp.hpp"
 
+using namespace std;
 using namespace cv;
 
 class CV_BRISKTest : public cvtest::BaseTest