devel/cld2: Fix build with Clang 6

cld_generated_cjk_uni_prop_80.cc:169:1: error: constant expression evaluates to -14 which cannot be narrowed to type 'CLD2::uint8' (aka 'unsigned char') [-Wc++11-narrowing]
-14,-14,-14,-14,-14,-14,-14,-14, -14,-14,-14,-14,-14,-14,-14,-14,
^~~
cld_generated_cjk_uni_prop_80.cc:169:1: note: insert an explicit cast to silence this issue
-14,-14,-14,-14,-14,-14,-14,-14, -14,-14,-14,-14,-14,-14,-14,-14,
^~~
static_cast<uint8>( )

http://beefy11.nyi.freebsd.org/data/head-i386-default/p477696_s338122/logs/errors/cld2-20150505.log

PR: 230906
Submitted by: tobik
Approved by: demon (maintainer)