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+

Why?

My understanding is that copy should work just fine for any file type, but copy_file will only work for true files (not links or directories). No?