[libc++] Enable <chrono> ""d and ""y literals for AppleClang 10 and up

AppleClang supports those literals starting in version 10.0.1.

llvm-svn: 368882
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 619172a8184ee6a1326588d916579fcabcfcf43a
3 files changed