Some bugfixes/added errors, convert most to not use simple_passthrough

tests/test_future.krak

@@ -0,0 +1,29 @@
+import future:*
+import io:*
+
+
+fun main() : int {
+    var a = 0
+    var c = fun() : int { 
+    var b = a
+    print("Thread ")
+    print(b)
+    println(" Started!")
+    var x : int = 0
+    for(var i = 1; i < 100; i++;) {
+        x++
+    }
+    return b
+    }
+    
+    var gadget1.construct(c) : future<int>
+    gadget1.run()
+    gadget1.finish()
+
+    println("Threads have finished")
+
+    pthread_exit()
+    println("All Done!")
+
+    return 0
+}