Kill the ImplSVGDIData::mbNoXORClipping flag

Instead, act as if it was true on all platforms. Don't do XOR clipping on any
platform. Simpler code is better code, and XOR tricks are generally very much
out of fashion these days, I have been told. Didn't seem to have any visible
ill effects on Linux at least.

Change-Id: I6192006c77a4a81363ec7b3292f72d512d5e9b53
Reviewed-on: https://gerrit.libreoffice.org/8901
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>
Tested-by: Chris Sherlock <chris.sherlock79@gmail.com>