Sunlight, Scrollblend, Water shader, Sunlight shadows

Effects improvements:
- Sunlight code cleaned up
- Normalmap scrollblend shader renamed to scrollblend, can be used on
regular surfaces now
- Removed r_shadows_drawafterrtlighting (not used anymore since there is
r_sunlight)
- Added r_shadows_drawaftertransparent  which makes transparent surfaces
to receive r_shadows 2 (only in shadowmapping mode)
- Added r_shadows_quantize_movement , r_shadows_quantize_throwdirection
to remove annoying shadow edge flickering effect of r_shadows 2
- Added r_shadows_focus2 (same as r_shadows_focus but in world space
coords)
- Stub cvars: r_sunlight_corona , r_sunlight_coronaintensity ,
r_sunlight_coronasize
- Q3Shader: dpwaterscroll have third parm which is strength of
distortion added do diffuse/gloss textures.
- Q3Shader: new dpscrollblend keyword (similar to dpwaterscroll, but 1
and 2 parms isn't transformed as "1/parm")