MakeTiles: when converting an SVG file, specify DPI rather than expected width/height

This way we can handle multi-tile SVG source files (e.g. for the larger zones) correctly.

git-svn-id: https://micropolis.googlecode.com/svn/trunk/micropolis-java@750 d9718cc8-9f43-0410-858b-315f434eb58c

src/micropolisj/build_tool/MakeTiles.java

@@ -182,8 +182,7 @@ public class MakeTiles
 
 		String [] cmdline = {
 			inkscapeBin.toString(),
-			"--export-width="+TILE_SIZE,
-			"--export-height="+TILE_SIZE,
+			"--export-dpi="+(TILE_SIZE*90.0/16.0),
 			"--export-png="+pngFile.toString(),
 			svgFile.toString()
 			};