clang-format: Avoid line-breaks that increase the current column.

While these might make sense for some rule (e.g. break after multi-line
operand), they generally appear ugly and confusing.

Before:
  fffffffffff(R\"x(
  multiline raw string literal xxxxxxxxxxxxxx
  )x\" + bbbbbb)

After:
  fffffffffff(R\"x(
  multiline raw string literal xxxxxxxxxxxxxx
  )x\" +
              bbbbbb)

llvm-svn: 204937