Temporarily revert:

Temporarily revert:

commit ae14bf6488e8441f0f6d74f00455555f6f3943ac
Author: Mehdi Amini <mehdi.amini@apple.com>
Date:   Fri Mar 11 17:15:50 2016 +0000

    Remove PreserveNames template parameter from IRBuilder

    Summary:
    Following r263086, we are now relying on a flag on the Context to
    discard Value names in release builds.

    Reviewers: chandlerc

    Subscribers: mzolotukhin, llvm-commits

    Differential Revision: http://reviews.llvm.org/D18023

    From: Mehdi Amini <mehdi.amini@apple.com>

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@263258
    91177308-0d34-0410-b5e6-96231b3b80d8

until we can figure out what to do about clang and Release build testing.

This reverts commit 263258.

llvm-svn: 263321