avoid exaggerated "using namespace"

lib/string_convs.cpp

@@ -13,7 +13,8 @@
 
 #include "string_convs.hpp"
 
-using namespace std;
+using std::string;
+using std::cout;
 using boost::format;
 
 //***************************************************************************//

lib/string_convs.hpp

@@ -7,17 +7,15 @@
 
 namespace triv {
 
-    using namespace std;
-
     // Convert to string:
-    string strg( bool val );
-    string strg( int val );
-    string strg( size_t val );
-    string strg( char val );
-    string strg( double val );
-    string time2strg( long seconds_since_the_epoch );
+    std::string strg( bool val );
+    std::string strg( int val );
+    std::string strg( size_t val );
+    std::string strg( char val );
+    std::string strg( double val );
+    std::string time2strg( long seconds_since_the_epoch );
 
     // Convert from string:
-    bool any2dbl( const string& inp, double *val );
-    bool any2int( const string& inp, int *val );
+    bool any2dbl( const std::string& inp, double *val );
+    bool any2int( const std::string& inp, int *val );
 }