<regex>: Revise parsing of escape sequences - #5380

<regex>: Revise parsing of escape sequences#5380

Stephan T. Lavavej (StephanTLavavej) merged 15 commits into

microsoft:mainmicrosoft/STL:mainfrom

muellerj2:regex-revise-escape-sequencesmuellerj2/STL:regex-revise-escape-sequencesCopy head branch name to clipboard