Fix creation of the TOC tree for dvi files

The old code assumed the number of children would be
"-NUMBER "
while this file has
"-NUMBER/"
so what we do now is looping after the - until we find a non digit
All this code would better be done using a regexp and not that many section calls
but i did not want to touch it more than needed

FIXED-IN: 4.7.3
(cherry picked from commit 83df127ac057d98e6e4f67e07074675c8830198a)