sw: hey, don't forget about big-endian parts in wrtasc.cxx!

Change-Id: I8e71c35dfb4f8ce475357412cc9121c50830069e
Reviewed-on: https://gerrit.libreoffice.org/8401
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>