Fix the build on i386 with clang 6.0.

kernel/qx11embed_x11.cpp:486:20: error: non-constant-expression cannot be narrowed from type 'unsigned int' to 'long' in initializer list [-Wc++11-narrowing]

long data[] = {XEMBED_VERSION, XEMBED_MAPPED};
               ^~~~~~~~~~~~~~

kernel/qx11embed_x11.cpp:486:20: note: insert an explicit cast to silence this issue

long data[] = {XEMBED_VERSION, XEMBED_MAPPED};
               ^~~~~~~~~~~~~~
               static_cast<long>( )

PR: 224945