fix fire coverage overlay by iterating over the whole map

[micropolis] / images / tiles-59.xpm

/* XPM */
static char *tiles___[] = {
/* columns rows colors chars-per-pixel */
"53 23 2 1",
"  c yellow",
". c gray69",
/* pixels */
".........    ........................................",
".....       . .......................................",
"....   . ...   ......................................",
".... .. .....    ....................................",
".... ..........     .................................",
"... ............   .  ...............................",
".  .. .. .......  .   ...............................",
"  ..  ..........  ..                              ...",
" .    ..........  ..                               ..",
"   .  .. .......  ................................  .",
"   .  ..........  .................................  ",
"   .  .. .......  ..                                 ",
"   .  .. .......  ..                                .",
"   .  ..........  ................................ ..",
"  .   .. .......  ..........    ......    ....    ...",
" . .  .. .......  ..        ....      ....    .......",
". .   ..........  .. ..... ..........................",
"..  . .. .......  .  ................................",
".... ... .......   ..................................",
".... ..........  ....................................",
".... .. .....  ......................................",
".....  . ... ........................................",
".........   ........................................."
};