Fix includes for histogram.h and reuse_distance.h

[snehasish]

Remove relative paths for includes in histogram.h and reuse_distance.h.

[fhahn]

run aarch64 tests

[fhahn]

Thank you very much for your patch. Could you explain which problem this fixes? Also, more files of drcachesim still have relative imports, e.g. https://github.com/DynamoRIO/dynamorio/blob/master/clients/drcachesim/reader/file_reader.h

[snehasish]

Apologies for the terse description.

This fix removes the relative paths so that when reusing code for internal tools at Google, we can specify includes via -I. At this time we are interested in exposing the histogram_t and reuse_distance_t tools only.

[derekbruening]

Looks good. We're holding off on merges to master until the Mac build is fixed -- and that fix (#2809) is unfortunately still sitting waiting for the Travis Mac queue...

[fhahn]

Great thanks! Seems the builds are fine, LGTM given @derekbruening does not have any objections

[derekbruening]

This won't affect Mac so we'll put this one through as #2809 will have to re-run anyway after removing the Mac PR tweak.

[fhahn]

Ok, @derekbruening are you doing the merge or should I? Not sure how github handles race conditions there :)

[derekbruening]

I did the merge and change the commit msg to make it part of #2006.