Move LiveRegUnits implementation into .cpp. Comment and format.

llvm-svn: 192621
diff --git a/llvm/lib/CodeGen/CMakeLists.txt b/llvm/lib/CodeGen/CMakeLists.txt
index a00df3b..5aa5a75 100644
--- a/llvm/lib/CodeGen/CMakeLists.txt
+++ b/llvm/lib/CodeGen/CMakeLists.txt
@@ -35,6 +35,7 @@
   LiveRangeCalc.cpp
   LiveRangeEdit.cpp
   LiveRegMatrix.cpp
+  LiveRegUnits.cpp
   LiveStackAnalysis.cpp
   LiveVariables.cpp
   LocalStackSlotAllocation.cpp