Add option to show small differences

LNT ignores small changes by default to save users from getting
excessive amount of results. However this is counter-productive when
trying to examine benchmarks where <1% change is significant.

The patch adds option to show small differences.


git-svn-id: https://llvm.org/svn/llvm-project/lnt/trunk@213124 91177308-0d34-0410-b5e6-96231b3b80d8
Show geomean for filtered tests

LNT shows geomean for all tests, even if user filters a subset of tests.

This patch lets LNT to calculate geomean for the chosen tests only.
Also it stores the comparison results to avoid computing aggregation
function twice.


git-svn-id: https://llvm.org/svn/llvm-project/lnt/trunk@213127 91177308-0d34-0410-b5e6-96231b3b80d8