On windows, show message box with help, as there is no stderr (fixes #702)

src/init.cpp

@@ -246,7 +246,12 @@ bool AppInit2(int argc, char* argv[])
 
         // Remove tabs
         strUsage.erase(std::remove(strUsage.begin(), strUsage.end(), '\t'), strUsage.end());
+#if defined(QT_GUI) && defined(WIN32)
+        // On windows, show a message box, as there is no stderr
+        wxMessageBox(strUsage, "Usage");
+#else
         fprintf(stderr, "%s", strUsage.c_str());
+#endif
         return false;
     }
 

src/qt/bitcoin.cpp

@@ -27,18 +27,10 @@ QSplashScreen *splashref;
 
 int MyMessageBox(const std::string& message, const std::string& caption, int style, wxWindow* parent, int x, int y)
 {
-    // Message from main thread
-    if(guiref)
-    {
-        guiref->error(QString::fromStdString(caption),
-                      QString::fromStdString(message));
-    }
-    else
-    {
-        QMessageBox::critical(0, QString::fromStdString(caption),
-            QString::fromStdString(message),
-            QMessageBox::Ok, QMessageBox::Ok);
-    }
+    // Message from AppInit2(), always in main thread before main window is constructed
+    QMessageBox::critical(0, QString::fromStdString(caption),
+        QString::fromStdString(message),
+        QMessageBox::Ok, QMessageBox::Ok);
     return 4;
 }