Don't render display name/chat message for own avatar in first person mode.
Use a spherical estimate of the shadowed region to avoid growing and shrinking
it as we turn around.  Also, might as well render shadows for the billboards.
Merge pull request #2561 from ey6es/master

Don't render display name for own avatar in first person mode, use a spherical model for the shadow volume to prevent growing and shrinking.