MacGui: simplify advanced widgets hide/show logic.
MacGui: simplify advanced widgets enable/disable logic.
MacGui: don't use the advanced panel for Libav encoders.
MacGui: cleanup after last commit.
MacGui: remove unused widgets.
MacGui: rename some advanced panel widgets.
MacGui: cleanup after last commit.
MacGui: rename some video panel widgets.
MacGui: re-indent after last commit.
MacGui: cleanup after last commit.
MacGui: move widgets around the video panel.
MacGui: cleanup after last commit.