Bump up version to 6.7.3

Update version to 6.6.4

Special release for ARM. (Note: the originally tagged commit for this…

… release was wrong but the tag has been updated a couple of times. You might need to delete your copy of the tag with `git tag -d v5.18.4` to get the new one. See https://git-scm.com/docs/git-tag#_on_re_tagging)

Update version to 6.6.3

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Bump up version to 6.5.3

Update history and version for 6.5.2

Making platform 007 (gcc 7) default in build_detect_platform.sh (face…

…book#5947)

Summary:
Making platform 007 (gcc 7) default in build_detect_platform.sh.
Pull Request resolved: facebook#5947

Differential Revision: D18038837

Pulled By: vjnadimpalli

fbshipit-source-id: 9ac2ddaa93bf328a416faec028970e039886378e

Bump up version to 6.3.6

Bump version to 6.2.4

Update HISTORY and bump version