Open namespace around definitions

While defining functions in another namespace is technically allowed as
long as the definition can be matched to a declaration, this can lead to
ambiguous resolutions, such as here (GAL vs KIGFX).

pcbnew/ratsnest_viewitem.cpp

@@ -35,7 +35,7 @@
 
 #include <boost/foreach.hpp>
 
-using namespace KIGFX;
+namespace KIGFX {
 
 RATSNEST_VIEWITEM::RATSNEST_VIEWITEM( RN_DATA* aData ) :
         EDA_ITEM( NOT_USED ), m_data( aData )
@@ -118,3 +118,5 @@ void RATSNEST_VIEWITEM::ViewGetLayers( int aLayers[], int& aCount ) const
     aCount = 1;
     aLayers[0] = ITEM_GAL_LAYER( RATSNEST_VISIBLE );
 }
+
+}