QObjectHelper: some optimizations
QObjectHelper: some optimizations

- cache end iterator in the loop how range-based for does.
- don't create QString from QL1S, just use overloaded operator==
  to compare two QL1S.
- reorder condition: QMetaProperty::isReadable() is cheaper than
  QStringList::contains().

flavio/qjson,drizt/qjson,coolshou/qjson,drizt/qjson,flavio/qjson,coolshou/qjson