Set optimizer options in WelsVP similarly to the other encoder projects
Remove stray optimization options from the WelsEncPlus project

There's not much performance critical code within this lib, all
the performance critical code in the encoder is in WelsEncCore and
WelsVP, so there's little point in having an extra odd option enabled
here.
Merge pull request #1132 from mstorsjo/unify-encoder-opts

Unify optimization options within the encoder MSVC projects