added support for function imports

trainride.cwa

@@ -0,0 +1,25 @@
+import "env.memory" memory(2);
+
+export fn tic(time: i32) {
+  let i: i32;
+  let defer t = time as f32 / 1000 as f32;
+  loop pixels {
+    let defer x = (i % 320 - 160) as f32;
+    let defer y = (i / 320) as f32 - 128.5;
+    let defer z = t + 20 as f32 / sqrt(x*x + y*y);
+    let defer z_int = z as i32;
+    let defer q = select(z_int % 9 >= 6, z, (z_int - z_int % 9 + 6) as f32);
+    let defer w = 9 as f32 / y + t;
+    let defer s = q - t;
+    let defer m = x * s / 50 as f32;
+
+    i?120 = select(y > 0 as f32 & w < q,
+              select(abs(x * (w - t)) < 9 as f32, 15, 7) - w as i32 % 2,
+              select(y * s > -99 as f32 / (m * m + 1 as f32),
+                select(q == z, z_int % 2, 3),
+                12 + (y / 23 as f32) as i32
+              )
+            ) * 16;
+    branch_if (i := i + 1) < 320*256: pixels;
+  }
+}