cleaned up R_RenderView setup code a bit, and shuffled SCR_CalcRefdef stuff to SCR_Up...

cleaned up R_RenderView setup code a bit, and shuffled SCR_CalcRefdef stuff to SCR_UpdateScreen
scissor is now on during all of R_RenderView (including rtlight portions), and GL_Scissor is used to set it instead of direct qglScissor calls, also GL_ScissorTest is used
r_farclip is now calculated without need for... just about anything, this allowed shuffling the setup code around a bit
various cleanups to allow multiple view renders per frame
added scr_zoomwindow cvars to do a (silly) zoomed view picture-in-picture overlay, it works but turned out useless in playtesting unless you want to stare at a shambler's chest... ugh
R_AnimateLight and R_BuildLightList merged to become R_UpdateLights
some setup code from R_RenderView became a new function R_UpdateWorld
GL_SetupView_ViewPort calls replaced by qglViewport calls, as it was a mostly useless wrapper

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@3919 d7cf8633-e32d-0410-b094-e92efae38249