fdo#39468 Translate German comments to English (vcl/inc/window.h)

Change-Id: I83a0e77f6399cdb4cac19ad14da6ea21b4a66969
Also: minor indentation fixes, and unnecessary comments removed
Reviewed-on: https://gerrit.libreoffice.org/7651
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>