OGLRender: prefer GL_LINE_LOOP rather than GL_QUADS for line segment.

Algorithm of isPolyLine() isn't perfect, but I think it'll work good enough for most cases.
This change should improve Castlevania Portrait of Ruin (trajectory of ricochet, and glow of warp stone)
SoftRasterizer must have a similar issue, it doesn't display both of them.

desmume/src/OGLRender.cpp

@@ -817,6 +817,64 @@ static void GL_ReadFramebuffer()
 #endif
 }
 
+// "Workaround" for line poly
+static bool isLinePoly(int listIndex)
+{
+	POLY *poly = &gfx3d.polylist->list[gfx3d.indexlist.list[listIndex]];
+	int type = poly->type;
+	VERT *vert1, *vert2;
+
+	if (type <= 2)
+		return true;
+	else if (type > 4)
+		return false;
+
+	// Method 1:
+	// Castlevania Portrait of Ruin - trajectory of ricochet
+	bool duplicatedVert[4] = { false, false, false, false };
+	for(int i = 0; i < type - 1; i++)
+	{
+		vert1 = &gfx3d.vertlist->list[poly->vertIndexes[i]];
+		for(int j = i + 1; j < type; j++)
+		{
+			vert2 = &gfx3d.vertlist->list[poly->vertIndexes[j]];
+			if (vert1->x == vert2->x && vert1->y == vert2->y)
+			{
+				duplicatedVert[j] = true;
+			}
+		}
+	}
+	int vertCount = type;
+	for(int i = 0; i < type; i++)
+	{
+		if (duplicatedVert[i])
+			vertCount--;
+	}
+	if (vertCount <= 2)
+		return true;
+
+	// Method 2:
+	// Castlevania Portrait of Ruin - warp stone
+	bool horizontalLine = true;
+	bool verticalLine = true;
+	vert1 = &gfx3d.vertlist->list[poly->vertIndexes[0]];
+	for(int i = 1; i < type && (horizontalLine || verticalLine); i++)
+	{
+		vert2 = &gfx3d.vertlist->list[poly->vertIndexes[i]];
+		if (vert1->coord[0] != vert2->coord[0])
+		{
+			verticalLine = false;
+		}
+		if (vert1->coord[1] != vert2->coord[1])
+		{
+			horizontalLine = false;
+		}
+	}
+	if (horizontalLine || verticalLine)
+		return true;
+
+	return false;
+}
 
 static void OGLRender()
 {
@@ -894,8 +952,11 @@ static void OGLRender()
 
 			float alpha = poly->getAlpha()/31.0f;
 			if(wireframe) alpha = 1.0;
+			bool linePoly = isLinePoly(i);
 
-			if (type == 4) 
+			if (linePoly)
+				glBegin(GL_LINE_LOOP);
+			else if (type == 4)
 				glBegin(GL_QUADS);
 			else
 				glBegin(GL_TRIANGLES);