Insert a new element in an Rd object possibly surrounding it with new lines.
Rdo_insert(rdo, val, newline = TRUE)an Rd object
an Rd object
the content to insert, an Rd object.
a logical value, controls the insertion of new lines
before and after val, see `Details'.
Georgi N. Boshnakov
Argument val is inserted in rdo at an appropriate
position, see Rdo_get_insert_pos for detailed
explanation.
If newline is TRUE, newline elements are inserted before and
after val but only if they are not already there.
Typically, val is a section of an Rd object and rdo is
an Rd object which is being constructed or modified.