Fixed a compiler warning on newest version of gcc

modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp

@@ -39,11 +39,13 @@
  #define __cdecl
 #endif
 
-namespace
+namespace Vst2
 {
 #include "juce_VSTInterface.h"
 }
 
+using namespace Vst2;
+
 #include "juce_VSTCommon.h"
 
 #if JUCE_MSVC