Cast inner type in OsStr::bytes

The innermost type is not [u8] on all platforms but is assumed to have
the same memory layout as [u8] since this conversion was done via
mem::transmute before.

Author: nvzqz

src/libstd/ffi/os_str.rs

@@ -520,7 +520,7 @@ impl OsStr {
     /// Note: it is *crucial* that this API is private, to avoid
     /// revealing the internal, platform-specific encodings.
     fn bytes(&self) -> &[u8] {
-        &self.inner.inner
+        unsafe { &*(&self.inner as *const _ as *const [u8]) }
     }
 }