\tabto{<length>} moves the typesetting position to <length>
from the left margin of the paragraph. If the typesetting
position is already further along, \tabto starts a new line;
the command \tabto* will move position backwards if necessary,
so that previous text may be overwritten. The command
\TabPositions may be used to define a set of tabbing positions,
after which the command \tab advances typesetting position to
the next defined 'tab stop'.
