perf diff: Make hist_entry_diff fields union
perf diff: Make hist_entry_diff fields union

The period_ratio_delta, period_ratio and wdiff are never by used at the
same time.  Instead, Just one of them is accessed according to a
comparison method.  So make it union to reduce memory footprint.

Signed-off-by: Namhyung Kim <5c915a589b3ddf58cebf14bec41bcc143b37ac3c@kernel.org>
Cc: David Ahern <b80c1600f604d3b0d768f26f90a76757e76005dd@gmail.com>
Cc: Jiri Olsa <2c6594f608aa3d41e98d48846a6328831f7084ad@redhat.com>
Cc: Peter Zijlstra <645ca7d3a8d3d4f60557176cd361ea8351edc32b@chello.nl>
Link: http://lkml.kernel.org/r/1429416255-12070-3-git-send-email-5c915a589b3ddf58cebf14bec41bcc143b37ac3c@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <293abb6b76d7791c0732cc517d38c4b5c734b87f@redhat.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs