Restore a bit of the non-deferred renderer's sun/moon waterglow in deferred rendering.  This also adds a slight pinch of glow to shiny sun-spots.  So be it.
(transplanted from 5a0d9e5b5cfb2ecd96685f0275ab8e999ab86263)
(transplanted from 90f0ce75b2d7bb9fc03e84245db27a16508cde63)