Swaps the value of this and second if second comes before
this in the buffer.
That is, ensures that this and second are in sequence. Most text buffer functions that
take a range call this automatically on your behalf, so there’s no real reason to call it yourself in those cases. There are some
exceptions, such as [[email protected]_range], that expect a pre-sorted range.
| this |
a `GtkTextIter` |
| second |
another `GtkTextIter` |