devel/ccdoc: Fix build with Clang 6

log.cc:236:8: error: invalid operands to binary expression ('std::1::ostream' (aka 'basic_ostream<char>') and 'std::1::ostream')

(*os) << fct( *os );
~~~~~ ^  ~~~~~~~~~~

http://beefy11.nyi.freebsd.org/data/head-i386-default/p477696_s338122/logs/errors/ccdoc-0.8r41.log