Pass known page breaks as const ref to wxHtmlDCRenderer::Render()

This method doesn't modify the known page breaks, it only uses them to
find the next one, so make it more clear by using const reference in the
function signature.

include/wx/html/htmprint.h

@@ -78,7 +78,7 @@ public:
     // set the same pagebreak twice.
     //
     // CAUTION! Render() changes DC's user scale and does NOT restore it!
-    int Render(int x, int y, wxArrayInt& known_pagebreaks, int from = 0,
+    int Render(int x, int y, const wxArrayInt& known_pagebreaks, int from = 0,
                int dont_render = false, int to = INT_MAX);
 
     // returns total width of the html document

src/html/htmprint.cpp

@@ -141,7 +141,7 @@ void wxHtmlDCRenderer::SetStandardFonts(int size,
 }
 
 int wxHtmlDCRenderer::Render(int x, int y,
-                             wxArrayInt& known_pagebreaks,
+                             const wxArrayInt& known_pagebreaks,
                              int from, int dont_render, int to)
 {
     wxCHECK_MSG( m_Cells, 0, "SetHtmlText() must be called before Render()" );