fairland: Reject continent size 1

fairland creates continents of size 1 just fine, but the newcap_script
it emits doesn't work: the newcap command requires a second wilderness
sector to the right of the first sector.

Reject continent size 1.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

src/util/fairland.c

@@ -397,8 +397,8 @@ parse_args(int argc, char *argv[])
     }
 
     sc = atoi(argv[1]);
-    if (sc < 1) {
-	fprintf(stderr, "%s: size of continents must be > 0\n",
+    if (sc < 2) {
+	fprintf(stderr, "%s: size of continents must be > 1\n",
 		program_name);
 	exit(1);
     }