Check that rows in wxDataViewListCtrl have the right size

Vectors passed to wxDataViewListCtrl::{Append,Insert,Prepend}Item()
functions must have the correct, i.e. equal to the column count, number
of items as otherwise accessing them later would result in a crash.

Add checks verifying that this is indeed the case.

Closes wxWidgets#724

src/common/datavcmn.cpp

@@ -2209,6 +2209,7 @@ wxString wxDataViewListStore::GetColumnType( unsigned int pos ) const
 
 void wxDataViewListStore::AppendItem( const wxVector<wxVariant> &values, wxUIntPtr data )
 {
+    wxCHECK_RET( values.size() == GetColumnCount(), "wrong number of values" );
     wxDataViewListStoreLine *line = new wxDataViewListStoreLine( data );
     line->m_values = values;
     m_data.push_back( line );
@@ -2218,6 +2219,7 @@ void wxDataViewListStore::AppendItem( const wxVector<wxVariant> &values, wxUIntP
 
 void wxDataViewListStore::PrependItem( const wxVector<wxVariant> &values, wxUIntPtr data )
 {
+    wxCHECK_RET( values.size() == GetColumnCount(), "wrong number of values" );
     wxDataViewListStoreLine *line = new wxDataViewListStoreLine( data );
     line->m_values = values;
     m_data.insert( m_data.begin(), line );
@@ -2228,6 +2230,7 @@ void wxDataViewListStore::PrependItem( const wxVector<wxVariant> &values, wxUInt
 void wxDataViewListStore::InsertItem(  unsigned int row, const wxVector<wxVariant> &values,
                                        wxUIntPtr data )
 {
+    wxCHECK_RET( values.size() == GetColumnCount(), "wrong number of values" );
     wxDataViewListStoreLine *line = new wxDataViewListStoreLine( data );
     line->m_values = values;
     m_data.insert( m_data.begin()+row, line );