Fixes issue #409: undefined behavior index entry.
Merge pull request #410 from godbyk/bugfix/undefined-behavior-index-entry

[istreambuf.iterator] Use "behavior, undefined" not "undefined behavior" for index entry as we do everywhere else.

Fixes #409
[unord.map.cnstr] Fix misapplication of edit for LWG2230.

Reported by Alisdair Meredith.