Change RGB32k to a union of BYTE[32][32][32] and BYTE[32*32*32]

- Clang's optional runtime array bounds checking doesn't understand when we
  intentionally "overflow" by doing this:
    RGB32k[0][0][colorval]
  It will warn that it was accessed at an index will past the bounds
  of type 'BYTE [32]', which makes it less than useful for catching real
  array bounds overflows. So now do this:
    RGB32k.All[colorval]
  And if you want this:
    RGB32k[r][g][b]
  Now do this:
    RGB32k.RGB[r][g][b]

src/v_draw.cpp

@@ -893,7 +893,7 @@ void DCanvas::PUTTRANSDOT (int xx, int yy, int basecolor, int level)
 	DWORD fg = fg2rgb[basecolor];
 	DWORD bg = bg2rgb[*spot];
 	bg = (fg+bg) | 0x1f07c1f;
-	*spot = RGB32k[0][0][bg&(bg>>15)];
+	*spot = RGB32k.All[bg&(bg>>15)];
 }
 
 void DCanvas::DrawLine(int x0, int y0, int x1, int y1, int palColor, uint32 realcolor)