graphics/gtimelapse: Unbreak build on FreeBSD >= 12.1

gtimelapse.cpp:753:2: error: reference to 'thread' is ambiguous

thread = CreateThread();
^

./globals.h:23:18: note: candidate found by name lookup is 'thread'
extern MyThread *thread;

^

/usr/include/c++/v1/__threading_support:397:24: note: candidate found by name lookup is 'std::__1::thread'
class _LIBCPP_TYPE_VIS thread;

^

http://beefy6.nyi.freebsd.org/data/121amd64-default/529299/logs/errors/gtimelapse-0.1_16.log