change cast to cast_ptr, take in ptr types

stdlib/conversions.krak

@@ -18,10 +18,10 @@ fun to_int<T>(in: T) : int {
 	}
 	return out;
 }
-fun cast<T,U>(in: T*):U* {
-    var out:U*
+fun cast_ptr<T,U>(in: T):U {
+    var out:U
         simple_passthrough(in:out:) """
-            void* out = (void*)in;
+            void* out = in;
         """
     return out
 }