sysutils/abgx360gui: Fix build with Clang 6

src/abgx360gui.cpp:2459:66: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]

str = wxT("Your StealthFiles folder is located here:"NEWLINE);
                                                     ^

beefy12.nyi.freebsd.org/data/head-amd64-default/p475964_s336959/logs/errors/abgx360gui-1.0.2_7.log