## Simpler syncer specs

This simplifies the syncer specs. The sequential syncer only is slightly improved, by changing

```
Definition synced R (f' f: val) :=
(□ ∀ P Q (x: val), ({{ R ★ P x }} f x {{ v, R ★ Q x v }}) →
({{ P x }} f' x {{ v, Q x v }}))%I.
```

such that `P`

, `Q`

don't factor in a dependency on `x`

any more. Since all three are quantified at the same time, the two specs are equivalent -- and the one where `P`

is not a predicate and `Q`

is exactly the postcondition is arguably simpler:

```
Definition synced R (f f': val) :=
(□ ∀ P Q (x: val), ({{ R ★ P }} f x {{ v, R ★ Q v }}) →
({{ P }} f' x {{ Q }}))%I.
```

For the atomic spec, the changes are deeper. The currying on some location `l`

is entirely removed. `is_atomic_syncer`

better mirrors `is_syncer`

from the sequential version. And finally, we use "original" atomic triples and not some modified version thereof (so `atomic_triple_base`

is killed).

TODO: Fix `atomic_pcas.v`

, it relied on the location currying done by `atomic_sync.v`

. However, I don't entirely grok that file. @zhangz could you give that a look?