devel/ncc: Fix build with Clang 6

preproc.C:275:7: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
"ncc "NCC_VERSION" - The new/next generation C compiler\n"

^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475478_s336801/logs/errors/ncc-2.8_2.log

nccnav.C:334:15: error: constant expression evaluates to -1 which cannot be narrowed to type 'unsigned int' [-Wc++11-narrowing]
} NoChunk = { ~0, ~0 };

^~