Take operator precedence into account when splitting lines.

Take operator precedence into account when splitting lines.

With this patch, splitting after binary operators has a panelty corresponding
to the operator's precedence. We used to ignore this and eagerly format like:

  if (aaaaaaaaaaaaaaaaaaaaaaaaa || bbbbbbbbbbbbbbbbbbbbbbbbb &&
      ccccccccccccccccccccccccc) { .. }

With this patch, this becomes:

  if (aaaaaaaaaaaaaaaaaaaaaaaaa ||
      bbbbbbbbbbbbbbbbbbbbbbbbb && ccccccccccccccccccccccccc) { .. }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171007 91177308-0d34-0410-b5e6-96231b3b80d8