devel/libopkele: Fix build with Clang 6

curl.cc:48:57: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]

|| (r=easy_setopt(CURLOPT_USERAGENT,PACKAGE_NAME"/"PACKAGE_SRC_VERSION))
                                                   ^

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p473790_s335878/logs/libopkele-2.0.4_12.log