Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/wasi-common/wasi-misc-tests/src/bin/big_random_buf.rs

@@ -0,0 +1,18 @@
+use wasi::wasi_unstable;
+
+fn test_big_random_buf() {
+    let mut buf = Vec::new();
+    buf.resize(1024, 0);
+    assert!(
+        wasi_unstable::random_get(&mut buf).is_ok(),
+        "calling get_random on a large buffer"
+    );
+    // Chances are pretty good that at least *one* byte will be non-zero in
+    // any meaningful random function producing 1024 u8 values.
+    assert!(buf.iter().any(|x| *x != 0), "random_get returned all zeros");
+}
+
+fn main() {
+    // Run the tests.
+    test_big_random_buf()
+}