Allow fixed indent of continuation lines

I propose adding an additional option for continuation line indent:

1. "Not at All"
2. "With Spaces"
3. "Regular Indent"
(new)4. "Fixed"

The "Fixed" indent would indent all continuation lines by one indent, relative to the current level:

void foo() {
    ...
    my_function(arg1,
        arg2,
        arg3);
   ...
   if (bar) {
        other_function(arg1,
            arg2,
            arg3);
    }
}

With this scheme, continuation lines are visually distinct, but their alignment does not change if "my_function" or "other_function" is renamed. Currently, continuation lines are aligned with the end of the previous entry:

...
    my_function(arg1,
                arg2,
                arg3);
...

This can cause trivial merge conflicts if one branch renames the function, and another renames only an argument.