Change scan3x to be LINE LINE DARK instead of LINE DARK DARK. This matches pictures of scanlines better and doubles the brightness as the old implementation was rather dark.

Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@4162

src/gui/render_templates.h

@@ -382,9 +382,9 @@ static void conc3d(Cache,SBPP,DBPP) (const void * s) {
 	line0[0]=P;				\
 	line0[1]=P;				\
 	line0[2]=P;				\
-	line1[0]=0;				\
-	line1[1]=0;				\
-	line1[2]=0;				\
+	line1[0]=P;				\
+	line1[1]=P;				\
+	line1[2]=P;				\
 	line2[0]=0;				\
 	line2[1]=0;				\
 	line2[2]=0;