DebugInfo: Rename generic unit references to "TheU" instead of TheCU now that they might be type units instead of compile units.

CR feedback from Eric Christopher on r196139.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196159 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unnecessary/commented-out header inclusion.

Review feedback from Eric Christopher on r196140

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196160 91177308-0d34-0410-b5e6-96231b3b80d8
Rename variables to be consistent (CST -> Cst). No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196161 91177308-0d34-0410-b5e6-96231b3b80d8
Move variables to where they are used and give them better names. No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196163 91177308-0d34-0410-b5e6-96231b3b80d8
Use local variable for repeated use rather than 'get' method. No functional change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196164 91177308-0d34-0410-b5e6-96231b3b80d8