Fixes for macosx 10.8

Changed -Wunused-private-field to -Wno-unused-private-field, now builds with Qt (iv)
Changed copy to copy_file to build with BOOST_FILESYSTEM_VERSION 3, in boost 1.46+

Hmmm, it's not available in namespace filesystem BUT in filesystem3, the following works:

boost::filesystem3::copy (from.str(), to.str(), ec);