Add more mixing packed and aligned to future possibilities

Author: Jules-Bertholet

text/3806-align-attr.md

@@ -363,7 +363,6 @@ fn foo(x: &u8) {
 2. Does MSVC do something weird with `alignas`? In other words, is the concern
    about `repr(C)` vs `repr(linear)` purely theoretical at this point, or does
    it matter in practice today?
-
 # Future possibilities
 [future-possibilities]: #future-possibilities
 
@@ -375,3 +374,6 @@ fn foo(x: &u8) {
 - We could add type-safe APIs for over-aligned pointers; for example,
   over-aligned reference types that are subtypes of `&`/`&mut`.
 - We could also add similar APIs for over-aligned function pointers.
+- We could loosen the restriction that fields of a `packed(n)` struct cannot
+  specify an alignment greater that `n`. (Apparently, some C compilers allow
+  something similar.)