Initial reorg.

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

crates/wasi-common/wasi-common-cbindgen/tests/test.rs

@@ -0,0 +1,9 @@
+#[test]
+fn tests() {
+    let t = trybuild::TestCases::new();
+    t.pass("tests/no_args.rs");
+    t.pass("tests/val_args.rs");
+    t.pass("tests/ref_args.rs");
+    t.pass("tests/mut_args.rs");
+    t.pass("tests/array_args.rs");
+}