Validate fullscreen related menu items

Entering/Exiting fullscreen (old Welly style) menu item will be
disabled in 10.7 fullscreen mode. Increase/Decrease font size menu
items will be disable in 10.7 fullscreen mode & old Welly style full
screen mode.
Rename old Welly style fullscreen mode to "Presentation Mode"

Now both 10.7 style full screen mode and old style presentation mode
can concurrently exist in menus