Ignore stdio mutex poison state

Nothing inside of the read/write interface itself can panic, so any
poison must have been the result of user code which the lock isn't
protecting.

src/libstd/io/stdio.rs

@@ -146,7 +146,7 @@ impl Stdin {
     /// accessing the underlying data.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn lock(&self) -> StdinLock {
-        StdinLock { inner: self.inner.lock().unwrap() }
+        StdinLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
     }
 
     /// Locks this handle and reads a line of input into the specified buffer.
@@ -249,7 +249,7 @@ impl Stdout {
     /// returned guard also implements the `Write` trait for writing data.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn lock(&self) -> StdoutLock {
-        StdoutLock { inner: self.inner.lock().unwrap() }
+        StdoutLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
     }
 }
 
@@ -319,7 +319,7 @@ impl Stderr {
     /// returned guard also implements the `Write` trait for writing data.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn lock(&self) -> StderrLock {
-        StderrLock { inner: self.inner.lock().unwrap() }
+        StderrLock { inner: self.inner.lock().unwrap_or_else(|e| e.into_inner()) }
     }
 }