Reverse the order of improvements in the output of compare_perf_tests

Both regressions and improvements are sorted by the delta, which in case
of improvements produces the reversed order due to negative values of
delta.
This change makes the improvements ordered 'naturally':
most-improved-first.

benchmark/scripts/compare_perf_tests.py

@@ -348,6 +348,7 @@ def sort_ratio_list(ratio_list, changes_only=False):
         complete_perf_list = (decreased_perf_list + increased_perf_list +
                               sorted_normal_perf_list)
 
+    increased_perf_list.reverse()
     return (complete_perf_list, increased_perf_list,
             decreased_perf_list, sorted_normal_perf_list)