The formats has been tested and verified on Mac OS X 10.8.5,
Mac OS X 10.11.5 and Ubuntu 14.04 LTS, all on x86_64 machines
and OSs. It mainly silences warnings. There were no warnings on
Ubuntu but a few on Mac OS, so the fix is intended to silence
warnings on Mac OS whithout triggering new warnings on other OSs.
Example of warnings previously encountered:
netutil.cc:2828:74: warning: format specifies type 'unsigned short'
but the argument has type 'int' [-Wformat]
0f22680426