Blind fix for wxTextDataObject trailing NUL under OS X.

Use the length provided to SetData() instead of assuming it is NUL-terminated.

Closes #9522.

(this is a backport of 20c130a578 from master)

docs/changes.txt

@@ -633,6 +633,7 @@ wxOSX:
 
 - Compilation fix for wxWebView under 10.10.
 - Fix conversion of wxBitmap to wxImage in 64 bit builds.
+- Fix length of text in wxTextDataObject.
 - Fix using wxHTTP and wxFTP from worker thread.
 - Fix wxFileDialog::GetFilterIndex() for file open dialogs (phsilva).
 - Fix custom paper support (tijsv).

src/common/dobjcmn.cpp

@@ -284,12 +284,12 @@ bool wxTextDataObject::GetDataHere(const wxDataFormat& format, void *buf) const
 }
 
 bool wxTextDataObject::SetData(const wxDataFormat& format,
-                               size_t WXUNUSED(len), const void *buf)
+                               size_t len, const void *buf)
 {
     if ( buf == NULL )
         return false;
 
-    wxWCharBuffer buffer = GetConv(format).cMB2WX( (const char*)buf );
+    wxWCharBuffer buffer = GetConv(format).cMB2WC((const char*)buf, len, NULL);
 
     SetText( buffer );