add nonpoison module and nonpoison mutex

Commits squashed from rust-lang#134663

Author: Aandreba

library/std/src/lib.rs

@@ -408,6 +408,7 @@
 #![feature(edition_panic)]
 #![feature(format_args_nl)]
 #![feature(log_syntax)]
+#![feature(nonpoison_mutex)]
 #![feature(test)]
 #![feature(trace_macros)]
 // tidy-alphabetical-end

library/std/src/sync/mod.rs

@@ -224,6 +224,8 @@ pub use self::poison::{MappedMutexGuard, MappedRwLockReadGuard, MappedRwLockWrit
 #[unstable(feature = "mpmc_channel", issue = "126840")]
 pub mod mpmc;
 pub mod mpsc;
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub mod nonpoison;
 
 #[unstable(feature = "sync_poison_mod", issue = "134646")]
 pub mod poison;

library/std/src/sync/nonpoison/mod.rs

@@ -0,0 +1,10 @@
+//! Non-poisoning syncronous locks.
+//!
+//! The locks found on this module will not become poisoned when a thread panics whilst holding a guard.
+
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub use self::mutex::MappedMutexGuard;
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub use self::mutex::{Mutex, MutexGuard};
+
+mod mutex;