Remove all trailing spaces

No real changes, just clean up sources by removing trailing spaces from
all the non-generated files.

This should hopefully avoid future commits mixing significant changes
with insignificant whitespace ones.

src/qt/listbox.cpp

@@ -182,7 +182,7 @@ unsigned wxListBox::GetCount() const
 }
 
 wxString wxListBox::GetString(unsigned int n) const
-{    
+{
     QListWidgetItem* item = m_qtListWidget->item(n);
     wxCHECK_MSG(item != NULL, wxString(), wxT("wrong listbox index") );
     return wxQtConvertString( item->text() );