Add NewGRF object properties to set viewport map mode/smallmap tile type

docs/landscape.html

@@ -1895,6 +1895,7 @@
      <li>m7: animation counter</li>
      <li style="color: blue">m4 bits 7..5: update counter (for objects using land ground sprites), incremented on every periodic processing.<BR>
          For snow and desert, these bits are not used, tile is updated on every periodic processing.</li>
+     <li style="color: blue">m4 bit 4: object type has viewport map colour/type override.</li>
      <li style="color: blue">m4 bits 3..2: ground type (for objects using land ground sprites):
       <table style="color: blue">
        <tr>