[Merge] ~daxtens/ubuntu/+source/glibc:xenial-math-perf-regression-1663280 into ubuntu/+source/glibc:ubuntu/xenial-devel

[Steve Langasek]

Review: Abstain

There are glibc SRUs in progress already behind the scenes, but they are not staged using these branches; so any review should be done by Adam directly.
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https://code.launchpad.net/~daxtens/ubuntu/+source/glibc/+git/glibc/+merge/356779
Your team Ubuntu Sponsors Team is requested to review the proposed merge of ~daxtens/ubuntu/+source/glibc:xenial-math-perf-regression-1663280 into ubuntu/+source/glibc:ubuntu/xenial-devel.