Fix errors in handling of maximum field in wxGenericProgressDialog.

Provide a SetMaximum() function for setting just m_maximum and return its
value from GetRange() instead of using m_gauge->GetRange() which doesn't work
when the native MSW version is used nor when the range is > USHRT_MAX under
MSW in any case.

More generally, this should fix a lot of bugs for progress dialogs using such
range as the values were not interpreted correctly in many places.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65506 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/progdlgg.h

@@ -67,7 +67,7 @@ public:
 
 protected:
     // This ctor is used by the native MSW implementation only.
-    wxGenericProgressDialog(wxWindow *parent, int maximum, int style);
+    wxGenericProgressDialog(wxWindow *parent, int style);
 
     void Create(const wxString& title,
                 const wxString& message,
@@ -75,6 +75,12 @@ protected:
                 wxWindow *parent,
                 int style);
 
+    // Update just the m_maximum field, this is used by public SetRange() but,
+    // unlike it, doesn't update the controls state. This makes it useful for
+    // both this class and its derived classes that don't use m_gauge to
+    // display progress.
+    void SetMaximum(int maximum);
+
     // Return the labels to use for showing the elapsed/estimated/remaining
     // times respectively.
     static wxString GetElapsedLabel() { return _("Elapsed time:"); }
@@ -144,7 +150,7 @@ private:
     static void SetTimeLabel(unsigned long val, wxStaticText *label);
 
     // common part of all ctors
-    void Init(wxWindow *parent, int maximum, int style);
+    void Init(wxWindow *parent, int style);
 
     // create the label with given text and another one to show the time nearby
     // as the next windows in the sizer, returns the created control