net/tcpreen: Fix build with Clang 6

main.cpp:111:27: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
"TCP re-engineering tool "VERSION" ("PACKAGE_HOST")\n"

^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p479076_s338486/logs/errors/tcpreen-1.4.4_3.log

PR: 230895
Submitted by: tobik
Approved by: jmohacsi@bsd.hu (maintainer timeout, 2 weeks)