Add line tracking support to FormattedStream 
- previously formatted_raw_ostream tracked columns, now it tracks lines too
- used by (upcoming) DebugIR pass to know the line number to connect to each IR
  instruction



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181463 91177308-0d34-0410-b5e6-96231b3b80d8