(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/station.cpp

@@ -125,8 +125,8 @@ void Station::MarkDirty() const
 		MarkAllViewportsDirty(
 			sign.left - 6,
 			sign.top,
-			sign.left + (sign.width_1 << 2) + 12,
-			sign.top + 48);
+			sign.left + ScaleByZoom(sign.width_1 + 12, _cur_dpi->zoom),
+			sign.top + ScaleByZoom(12, _cur_dpi->zoom));
 	}
 }