Bug#1093905: rust-cxx: please update to v1.0.122

[Chris Hofstaedtler]

Source: rust-cxx
Version: 1.0.87

I'd like to use Debian crates to build pdns and pdns-recursor, but
they need cxx (and cxx-build) 1.0.122. Please update cxx (and
cxx-build).

Thanks,
Chris