clang-format: Slightly change indentation rules in for loops.

There was already a TODO to double-check whether the extra indenation
makes sense. A slightly different case reveals that it is actively harmful:

  for (int i = 0; i < aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ||
                      bbbbbbbbbbbbbbbbbbbb < ccccccccccccccc;
       ++i) {
  }

Here (and it is probably not a totally infrequent case, it just works out that
"i < " is four spaces and so the four space extra indentation makes the
operator precedence confusing. So, this will now instead be formatted
as:

  for (int i = 0; i < aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa ||
                  bbbbbbbbbbbbbbbbbbbb < ccccccccccccccc;
       ++i) {
  }

llvm-svn: 231461