Change fairland island size probability distribution

Island size is randomly chosen from the interval [1..2*is+1], with
expected value is.  Use two dice to roll the size instead of one.
This makes extreme sizes much less likely.
(cherry picked from commit 29d2f5ccfe4d629151c4843f994ac8e9fcc74f58)

diff --git a/src/util/fairland.c b/src/util/fairland.c
index 3255d417661a46df22fc1056a4981c5ebce007b1..422a26dbc1d98603fb87ac79ca9a803ad36cd194 100644 (file)
--- a/src/util/fairland.c
+++ b/src/util/fairland.c
@@ -809,7 +809,7 @@ grow_islands(void)
        secs = 0;
        if (!place_island(c, &x, &y))
            return;
-       isiz = 1 + rnd(2 * is - 1);
+       isiz = 1 + rnd(is) + rnd(is);
        do {
            ++secs;
            find_coast(c);