[llvm] Sync DebugInfo.h with DebugInfoFlags.def

Command to see the differences:
  diff -u <(sed -n 's#^HANDLE_DI_FLAG *([^,]*, *\([^()]*\)) *\(//.*\)\?$#\1#p' <llvm/include/llvm/IR/DebugInfoFlags.def | grep -vw Largest) <(sed -n 's#^ *LLVMDIFlag\([^ ]*\) *= (\?[0-9].*$#\1#p' <llvm/include/llvm-c/DebugInfo.h)

OCaml binding is more seriously out of sync but I have not tried to sync it.

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D103910