introduce ir nop to fix loop bugs

examples/ack.pork

@@ -0,0 +1,17 @@
+/* ackermann function */
+func ack(m: int32, n: int32): int32 {
+  if m == 0 {
+    return n + 1
+  }
+
+  if n == 0 {
+    return ack(m - 1, 1)
+  }
+
+  return ack(m - 1, ack(m, n - 1))
+}
+
+export func main() {
+  let result: int32 = ack(3, 1)
+  println(result)
+}

examples/ffi.pork

@@ -1,14 +1,7 @@
 import std ffi.struct
 
-export let timeval = ffiStructDefine(
-  "long", "seconds",
-  "unsigned int", "microseconds"
-)
-
-export let timezone = ffiStructDefine(
-  "int", "minutes_greenwich",
-  "int", "dst_time"
-)
+export type timeval = native ffi "long" "seconds" "unsigned int" "microseconds"
+export type timezone = native ffi "int" "minutes_greenwich" "int" "dst_time"
 
 func gettimeofday(value, tz)
   native ffi "c" "int gettimeofday(struct timeval*, struct timezone*)"

examples/fib.pork

@@ -8,6 +8,6 @@ func fib(n: int32): int32 {
 }
 
 export func main() {
-  let result: int32 = fib(28)
+  let result: int32 = fib(31)
   println(result)
 }