Remove ErrorDialog.h from .h files (one function moves out of line)

src/commands/CommandTargets.cpp

@@ -27,6 +27,7 @@ capture the more lengthy output from some commands.
 #include <wx/string.h>
 #include "../ShuttleGui.h"
 #include "../Project.h"
+#include "../widgets/ErrorDialog.h"
 
 void CommandMessageTarget::StartArray()
 {
@@ -237,6 +238,12 @@ void BriefCommandMessageTarget::EndField(){
 }
 
 
+void MessageBoxTarget::Update(const wxString &message)
+{
+   AudacityMessageBox(message);
+}
+
+
 LispifiedCommandOutputTargets::LispifiedCommandOutputTargets( CommandOutputTargets & target )
  : CommandOutputTargets() ,
    pToRestore( &target )