Now that we've sorted out which bits are rightfully internal (see commit
7a4064cf87d23bffac987b3e39bf87d9b4d158fc), and which bits need a
comparison operator, rename IsEqual to operator==.

Change-Id: Iec229a7571d76ee18fbc0a4fe672cc2e50a44948
Reviewed-on: https://gerrit.libreoffice.org/42851Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>