constexpr applied to <complex>.

llvm-svn: 160585
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: f4e11de8e8495aa4e4ea649a9a2ed7c48dede7da
11 files changed