c++ backend: fixed double colon namespace syntax when used multiple times per line.
c++ backend: fixed double colon namespace syntax when used multiple times per line.

pombredanne/Rusthon,rusthon/Rusthon,secureosv/pythia,pombredanne/Rusthon,secureosv/pythia,secureosv/pythia,rusthon/Rusthon,secureosv/pythia,pombredanne/Rusthon,secureosv/pythia,rusthon/Rusthon,rusthon/Rusthon,rusthon/Rusthon,pombredanne/Rusthon,pombredanne/Rusthon