[codeview] Optimize the size of defranges with gaps

For small, discontiguous local variable regions, CodeView can use a
single defrange record with a gap, rather than having two defrange
records. I expect that this optimization will only have a minor impact
on debug info size.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281664 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed