Test cases

- Fixed `simple_function_decls.t` to include the required (but missing) `return` statement

source/tlang/testing/simple_function_decls.t

@@ -6,9 +6,13 @@ int k = 22;
 int apple(int arg1, int arg2)
 {
     int h = 69;
+    
+    return 0;
 }
 
 int banana(int arg1)
 {
     int h = 64;
+
+    return 0;
 }