Bugfix: For some reason, lines which were fed to EKHTML were broken
into parts.

It looks like EKHTML internally has a buffer where it copies data to,
such that in certain circumstances cb_data() still was called with
incomplete lines.  This here is another fix for this.  It perhaps
still isn't perfect, as this should be fixed in cb_data() and not in
the call to EKTHML.  (However fixing it in cb_data() needs a lot of
rewrite.)  For now it seems to work as expected.

Also tinohtmlabsurl.sh has now the ability to send non-URL lines to
some file descriptor (like /dev/null).
