Allow specifying the maximum width of static text in dialogs

This patch allows specification of the maximum width of static texts
created with wxDialog::CreateTextSizer.

The patch preserves backwards compatibility by setting the previous
width value as the default argument value.

Closes https://github.com/wxWidgets/wxWidgets/pull/355

include/wx/dialog.h

@@ -116,13 +116,15 @@ public:
 
 #if wxUSE_STATTEXT // && wxUSE_TEXTCTRL
     // splits text up at newlines and places the lines into a vertical
-    // wxBoxSizer
-    wxSizer *CreateTextSizer( const wxString& message );
+    // wxBoxSizer, with the given maximum width, lines will not be wrapped
+    // for negative values of widthMax
+    wxSizer *CreateTextSizer(const wxString& message, int widthMax = -1);
 
     // same as above but uses a customized wxTextSizerWrapper to create
     // non-standard controls for the lines
-    wxSizer *CreateTextSizer( const wxString& message,
-                              wxTextSizerWrapper& wrapper );
+    wxSizer *CreateTextSizer(const wxString& message,
+                             wxTextSizerWrapper& wrapper,
+                             int widthMax = -1);
 #endif // wxUSE_STATTEXT // && wxUSE_TEXTCTRL
 
     // returns a horizontal wxBoxSizer containing the given buttons