[ADT] Teach PointerUnion to support assignment directly from nullptr to
clear it out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207471 91177308-0d34-0410-b5e6-96231b3b80d8
Fix 80-columns, tab characters, and comments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207472 91177308-0d34-0410-b5e6-96231b3b80d8
80-column, tab characters, comment fixups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207473 91177308-0d34-0410-b5e6-96231b3b80d8
80-column fixups.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207474 91177308-0d34-0410-b5e6-96231b3b80d8
None of these targets actually define their own CFI_INSTRUCTION
opcode so there's no reason to use the target namespace for it
rather than TargetOpcode.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@207475 91177308-0d34-0410-b5e6-96231b3b80d8