vcl: tabify include/vcl/window.hxx

Change-Id: I2c45b3b125b758dd391376bf731d8b91c00a0a5d
Reviewed-on: https://gerrit.libreoffice.org/12337
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>
Tested-by: Chris Sherlock <chris.sherlock79@gmail.com>