Fix managment of layer 0 as bounding box in GdsParser.

* Bug: In GdsParser::readStructure(), the Gds::Layer_0_IsBoundary flag
    was not taken into account. The abutment box was always forced to
    the bounding box, resulting in incorrect cell size (and placement).

crlcore/src/ccore/gds/GdsParser.cpp

@@ -963,9 +963,11 @@ namespace {
 
     if (_validSyntax) _stream >> _record;
 
+    if (not useLayer0AsBoundary()) {
       UpdateSession::close();
       _cell->setAbutmentBox( _cell->getBoundingBox() );
       UpdateSession::open();
+    }
     _cell = NULL;
     cdebug_log(101,-1) << "    GdsStream::readStructure() - return:" << _validSyntax << endl;