fixed bug with asInteger on ZString.

ZString.cpp

@@ -137,7 +137,7 @@ namespace coreutils {
 	   ++cursor;
       if(cursor == end)
 	return 0;
-      while((*cursor >- '0') && (*cursor <= '9')) {
+      while((*cursor >= '0') && (*cursor <= '9')) {
 	 value *= 10;
 	 value += *cursor - 48;
 	 ++cursor;