[SCEV] Comment and whitesapce changes in header

 - Use doxygen-style comments
 - Don't repeat member names in comments
 - Add newlines between declarations

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@271154 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed