Provide an API to temporarily suppress DebugLocations from being attached
to emitted instructions.  Use this if you want an instruction to be
counted towards the prologue or if there is no useful source location.

rdar://problem/13442648

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180929 91177308-0d34-0410-b5e6-96231b3b80d8