Where we can prove that the virtual method is never overriden.
In the case of pure-virtual methods, we remove the method entirely.
Sometimes this leads to entire methods and fields being
eliminated.
Change-Id: I138ef81c95f115dbd8c023a83cfc7e9d5d6d14ae
...mostly done with a rewriting Clang plugin, with just some manual tweaking
necessary to fix poor macro usage.
Change-Id: Ie656f9d653fc716f72ac175925272696d509038f
see https://gerrit.libreoffice.org/#/c/3367/
and Change-Id: I00c96fa77d04b33a6f8c8cd3490dfcd9bdc9e84a for details
Change-Id: I199a75bc4042af20817265d5ef85b1134a96ff5a
