API guard every post-21 API.

This was generated mechanically by reverting my recent re-hide commits
(except for mempcpy, but versioner cleaned that up for me anyway),
reverting the commits which removed versioner, then:

```
m out/soong/ndk_headers.timestamp
cp -r out/soong/ndk/sysroot/usr/include/* bionic/libc/include
git -C bionic clean -df
```

Effectively, this has restored the `versioner` processed headers, but
I'm checking the results of that in so we don't have to keep
`versioner` around.

For the NDK, this restores r27 behavior by default. Anyone that's
opted into weak APIs will get the new behavior. I think this is our
best option. Anyone writing code with Android in mind should be using
weak APIs, but any code being lightly ported (and thus using the
default configuration) should not be, and it's those ports where we're
having trouble with collisions.

Bug: https://github.com/android/ndk/issues/2081
Test: None
Change-Id: I370079d27566b0c1543fb5890c958c8d09b05006
diff --git a/libc/include/sys/msg.h b/libc/include/sys/msg.h
index 26071b1..8b619be 100644
--- a/libc/include/sys/msg.h
+++ b/libc/include/sys/msg.h
@@ -46,6 +46,8 @@
 typedef __kernel_ulong_t msglen_t;
 
 /** Not useful on Android; disallowed by SELinux. */
+
+#if __BIONIC_AVAILABILITY_GUARD(26)
 int msgctl(int __msg_id, int __op, struct msqid_ds* _Nullable __buf) __INTRODUCED_IN(26);
 /** Not useful on Android; disallowed by SELinux. */
 int msgget(key_t __key, int __flags) __INTRODUCED_IN(26);
@@ -53,5 +55,7 @@
 ssize_t msgrcv(int __msg_id, void* _Nonnull __msgbuf_ptr, size_t __size, long __type, int __flags) __INTRODUCED_IN(26);
 /** Not useful on Android; disallowed by SELinux. */
 int msgsnd(int __msg_id, const void* _Nonnull __msgbuf_ptr, size_t __size, int __flags) __INTRODUCED_IN(26);
+#endif /* __BIONIC_AVAILABILITY_GUARD(26) */
+
 
 __END_DECLS