Update isKilledAt in TwoAddressInstructionPass.cpp to use LiveIntervals when
available.

With this commit there are no longer any assertion or verifier failures when
running 'make check' without LiveVariables. There are still 56 failing tests
with codegen differences and 1 unexpectedly passing test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175719 91177308-0d34-0410-b5e6-96231b3b80d8