Remove BROKEN_sparc64 statement which was originally added in r277772 by
linimon@ 6.5 years ago for Snappy 1.0.2. It now builds and runs fine on
10.4-STABLE running under QEMU 2.9.0 (regression tests pass, courtesy of
TEST_TARGET). While at it, move OPTIONS_DEFINE knob where it is usually
expected to be found in the Makefile.