Add V_DrawTutorialBack for drawing a console-like background box, add Lorem ipsum as filler test

src/v_video.c

@@ -1480,6 +1480,25 @@ void V_DrawFadeConsBack(INT32 plines)
 		*buf = consolebgmap[*buf];
 }
 
+// Very similar to F_DrawFadeConsBack, except we draw from the middle(-ish) of the screen to the bottom.
+void V_DrawTutorialBack(void)
+{
+	INT32 charheight = 8*vid.dupy;
+	UINT8 *deststop, *buf;
+
+#ifdef HWRENDER
+	if (rendermode != render_soft) // no support for OpenGL yet
+		return;
+#endif
+
+	// heavily simplified -- we don't need to know x or y position,
+	// just the start and stop positions
+	deststop = screens[0] + vid.rowbytes * vid.height;
+	buf = deststop - vid.rowbytes * ((charheight * 4) + (charheight/2)*5); // 4 lines of space plus gaps between and some leeway
+	for (; buf < deststop; ++buf)
+		*buf = consolebgmap[*buf];
+}
+
 // Gets string colormap, used for 0x80 color codes
 //
 static const UINT8 *V_GetStringColormap(INT32 colorflags)

src/v_video.h

@@ -158,6 +158,7 @@ void V_DrawFlatFill(INT32 x, INT32 y, INT32 w, INT32 h, lumpnum_t flatnum);
 void V_DrawFadeScreen(UINT16 color, UINT8 strength);
 
 void V_DrawFadeConsBack(INT32 plines);
+void V_DrawTutorialBack(void);
 
 // draw a single character
 void V_DrawCharacter(INT32 x, INT32 y, INT32 c, boolean lowercaseallowed);