add "install" target to Makefile

[micropolis] / images / tiles-153.xpm

/* XPM */
static char *tiles____[] = {
/* columns rows colors chars-per-pixel */
"126 2 2 1",
"  c #3F3F3F3F3F3F",
". c gray75",
/* pixels */
"                                                                                                                             .",
" ............................................................................................................................."
};