More of P0600; marking allocation routines as [[nodiscard]]

llvm-svn: 318992
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 3fddff51ba2b4d713dad95ca97681f004dc822c9
6 files changed