x11/wbar: Unbreak build with Clang 6

./src/core/Main.cc:84:38: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]

command = PACKAGE_NAME" "DEFAULT_ARGV;
                         ^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p474767_s336359/logs/wbar-2.3.4_1.log
http://thunderx1.nyi.freebsd.org/data/head-arm64-default/p474481_s336216/logs/wbar-2.3.4_1.log