Remove using std::XXX from headers

This is a bad practice to have using in headers because it pollutes the
namespace of any user of that header.
diff --git a/parameter/ParameterMgr.cpp b/parameter/ParameterMgr.cpp
index 32082b3..0101dfb 100644
--- a/parameter/ParameterMgr.cpp
+++ b/parameter/ParameterMgr.cpp
@@ -90,6 +90,11 @@
 
 #define base CElement
 
+using std::string;
+using std::list;
+using std::vector;
+using std::ostringstream;
+
 // Used for remote processor server creation
 typedef IRemoteProcessorServerInterface* (*CreateRemoteProcessorServer)(uint16_t uiPort, IRemoteCommandHandler* pCommandHandler);
 
@@ -1187,7 +1192,7 @@
     }
 
     // Build configurable element path list
-    vector<string> astrNewElementSequence;
+    std::vector<string> astrNewElementSequence;
 
     uint32_t uiArgument;