Hack to fix infitely tall software double sided linedefs flicker bug on some maps

Thanks Alug for looking into this.

Unfornately not easy to fix unless convert a bunch of code to use 64bit math or floats.

src/r_segs.cpp

@@ -1364,6 +1364,15 @@ static void R_RenderSegLoop (drawcolumndata_t* dc)
 		if (yl < top)
 			yl = top;
 
+		// insanely shitty hack to fix flickering on some maps
+		// for god knows why, on secret slide the renderer assumes some double sided linedefs have insanely tall walls
+		// since such tall walls are effectively nonsense in any case
+		// just skip them
+		if (yl > FRACUNIT*3)
+		{
+			continue;
+		}
+
 		if (markceiling)
 		{
 #if 0