Revert "Remove the explicit SDNodeIterator::operator= in favor of the implicit default"

Accidentally committed a few more of these cleanup changes than
intended. Still breaking these out & tidying them up.

This reverts commit r231135.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231136 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/LiveInterval.cpp

@@ -743,6 +743,7 @@ void LiveRange::flushSegmentSet() {
       segments.empty() &&
       "segment set can be used only initially before switching to the array");
   segments.append(segmentSet->begin(), segmentSet->end());
+  delete segmentSet;
   segmentSet = nullptr;
   verify();
 }