This subroutine is used by the transposition commands.
This function exchanges two nonoverlapping portions of the buffer. Arguments start1 and end1 specify the bounds of one portion and arguments start2 and end2 specify the bounds of the other portion.
transpose-regionsrelocates markers with the transposed text; a marker previously positioned within one of the two transposed portions moves along with that portion, thus remaining between the same two characters in their new position. However, if leave-markers is non-
transpose-regionsdoes not do this—it leaves all markers unrelocated.