Extract key to avoid preemptive mallocs in insert/emplace in associative containers

Summary: This patch applies Duncan's work on __hash_table to __tree.

Reviewers: mclow.lists, dexonsmith

Subscribers: dexonsmith, cfe-commits

Differential Revision: http://reviews.llvm.org/D18637

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@266491 91177308-0d34-0410-b5e6-96231b3b80d8
17 files changed