Make IsCheckable true by default and switch to explicitly disallowing it

Also add a new accessor to wxAuiToolBarItem to make it easier to
determine when a tool can be checked.

include/wx/event.h

@@ -2891,12 +2891,11 @@ public:
         m_setEnabled =
         m_setShown =
         m_setText =
-        m_setChecked =
-        m_isCheckable = false;
+        m_setChecked = false;
+        m_isCheckable = true;
     }
     wxUpdateUIEvent(const wxUpdateUIEvent& event)
         : wxCommandEvent(event),
-          m_isCheckable(event.m_isCheckable),
           m_checked(event.m_checked),
           m_enabled(event.m_enabled),
           m_shown(event.m_shown),
@@ -2904,6 +2903,7 @@ public:
           m_setShown(event.m_setShown),
           m_setText(event.m_setText),
           m_setChecked(event.m_setChecked),
+          m_isCheckable(event.m_isCheckable),
           m_text(event.m_text)
     { }
 
@@ -2921,9 +2921,9 @@ public:
     void Show(bool show) { m_shown = show; m_setShown = true; }
     void SetText(const wxString& text) { m_text = text; m_setText = true; }
 
-    // Set a flag saying if the object being updated supports the check action
+    // A flag saying if the item can be checked. True by default.
     bool IsCheckable() const { return m_isCheckable; }
-    void SetIsCheckable(bool aCheckable) { m_isCheckable = aCheckable; }
+    void DisallowCheck() { m_isCheckable = false; }
 
     // Sets the interval between updates in milliseconds.
     // Set to -1 to disable updates, or to 0 to update as frequently as possible.
@@ -2950,7 +2950,6 @@ public:
     virtual wxEvent *Clone() const wxOVERRIDE { return new wxUpdateUIEvent(*this); }
 
 protected:
-    bool          m_isCheckable;
     bool          m_checked;
     bool          m_enabled;
     bool          m_shown;
@@ -2958,6 +2957,7 @@ protected:
     bool          m_setShown;
     bool          m_setText;
     bool          m_setChecked;
+    bool          m_isCheckable;
     wxString      m_text;
 #if wxUSE_LONGLONG
     static wxLongLong       sm_lastUpdate;