Usage: <tt>input = [ <i>dsx dsy dsz</i> ] movefixedatoms </tt>

<p>
Add <tt><i>dsx, dsy, dsz</i></tt> to the scaled coordinates <tt>SR[i]</tt> of
all atoms <tt>i</tt> whose <tt>fixed[i] == 1</tt>.

<p>
Also see <tt>fixatoms_by_pos_topol</tt>, <tt>fixatoms_by_ID</tt>, <tt>removefixedatoms</tt>.

