... because that calls CompressRedlines, which may combine the new
redline with a previous one.

In that case, the part of the new redline that follows the currently
handled overlap cannot be checked for overlaps with subsequent existing
redlines.

So prevent this with a new flag m_isForbidCompressRedlines and instead
call CompressRedlines() at the end of AppendRedline().

Change-Id: I7567962c31366ded9a433a13232d3db985745e43
Reviewed-on: https://gerrit.libreoffice.org/36901Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>