Fixed some errors and warnings when building with JUCE_DLL_BUILD=1

modules/juce_core/text/juce_String.h

@@ -1348,7 +1348,7 @@ JUCE_API String& JUCE_CALLTYPE operator<< (String& string1, double number);
 
 // Automatically creating a String from a bool opens up lots of nasty type conversion edge cases.
 // If you want a String representation of a bool you can cast the bool to an int first.
-JUCE_API String& JUCE_CALLTYPE operator<< (String&, bool) = delete;
+String& JUCE_CALLTYPE operator<< (String&, bool) = delete;
 
 //==============================================================================
 /** Case-sensitive comparison of two strings. */

modules/juce_gui_basics/widgets/juce_Slider.cpp

@@ -27,7 +27,8 @@
 namespace juce
 {
 
-class Slider::Pimpl   : private AsyncUpdater,
+class Slider::Pimpl   : public AsyncUpdater, // this needs to be public otherwise it will cause an
+                                             // error when JUCE_DLL_BUILD=1
                         private Button::Listener,
                         private Label::Listener,
                         private Value::Listener

modules/juce_gui_basics/windows/juce_DialogWindow.h

@@ -144,6 +144,8 @@ public:
         */
         int runModal();
        #endif
+
+        JUCE_DECLARE_NON_COPYABLE (LaunchOptions)
     };
 
     //==============================================================================