experimental: remove dead function
experimental: remove dead function

This template was defined inline, within the TU only and had no uses
across the entire repository.  Remove the dead code.  NFC.

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@293445 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx