Revert "LiveIntervalAnalysis: Remove LiveVariables requirement" and LiveIntervalTest

The commit breaks stage2 compilation on PowerPC. Reverting for now while
this is analyzed. I also have to revert the LiveIntervalTest for now as
that depends on this commit.

Revert "LiveIntervalAnalysis: Remove LiveVariables requirement"
This reverts commit r260806.
Revert "Remove an unnecessary std::move to fix -Wpessimizing-move warning."
This reverts commit r260931.
Revert "Fix typo in LiveIntervalTest"
This reverts commit r260907.
Revert "Add unittest for LiveIntervalAnalysis::handleMove()"
This reverts commit r260905.

llvm-svn: 261189