(svn r9884) -Feature: 2 new zoom-out levels: 8 times and 16 times

-Codechange: unified the blitter function so we have 1 function for all zoom-levels
-Codechange: make most of the label functions work with zoom-level instead of magic numbers and big switches per zoom-level
-Codechange: MakeXXXDirty() functions didn't take into account zoom-level, but just used the biggest possible value
-Codechange: simplified blitter functions to avoid code duplication

src/signs.cpp

@@ -67,8 +67,8 @@ static void MarkSignDirty(Sign *si)
 	MarkAllViewportsDirty(
 		si->sign.left - 6,
 		si->sign.top  - 3,
-		si->sign.left + si->sign.width_1 * 4 + 12,
-		si->sign.top  + 45);
+		si->sign.left + ScaleByZoom(si->sign.width_1 + 12, _cur_dpi->zoom),
+		si->sign.top  + ScaleByZoom(12, _cur_dpi->zoom));
 }
 
 /**