Add __isOSVersionAtLeast and __isPlatformVersionAtLeast symbols

Allows users to link to Objective-C code using `@available(...)`.

Author: madsmtm

library/std/src/lib.rs

@@ -347,6 +347,7 @@
 #![feature(hasher_prefixfree_extras)]
 #![feature(hashmap_internals)]
 #![feature(hint_must_use)]
+#![feature(int_from_ascii)]
 #![feature(ip)]
 #![feature(lazy_get)]
 #![feature(maybe_uninit_slice)]
@@ -362,6 +363,7 @@
 #![feature(slice_internals)]
 #![feature(slice_ptr_get)]
 #![feature(slice_range)]
+#![feature(slice_split_once)]
 #![feature(std_internals)]
 #![feature(str_internals)]
 #![feature(strict_provenance_atomic_ptr)]

library/std/src/sys/mod.rs

@@ -21,6 +21,7 @@ pub mod io;
 pub mod net;
 pub mod os_str;
 pub mod path;
+pub mod platform_version;
 pub mod process;
 pub mod random;
 pub mod stdio;