implement a more c++-style TFRewrite alternative

implement a more c++-style TFRewrite alternative

TFRewrite is okay, but it has obscure limitations (256 Tags), even more
obscure bugs (order for renames is defined by the old name) and the
interface is very c-style encouraging bad usage like we do it in
apt-ftparchive passing massive amounts of c_str() from std::string in.

The old-style is marked as deprecated accordingly. The next commit will
fix all places in the apt code to not use the old-style anymore.