typo fixes

Author: steveklabnik

_posts/2017-10-12-Rust-1.21.md

@@ -106,7 +106,7 @@ preview, and you'll hear more about these plans in the future.
 
 Finally, a few documentation improvements. First up, if you visit [the docs
 for `std::os`](https://doc.rust-lang.org/stable/std/os/), which contains
-operating-system specific functionality, you'll now see more than just `linux`,
+operating system specific functionality, you'll now see more than just `linux`,
 the platform we build the documentation on. We've long regretted that the hosted
 version of the documentation has been Linux-specific; this is a first step towards
 rectifying that. This is [specific to the standard
@@ -161,7 +161,7 @@ for i in 0..10 {
 ```
 
 The correct one to use depends on your situation; in the sample above, the `for` loop
-is pretty striaghtforward. But when you're chaining a number of iterators together,
+is pretty straightforward. But when you're chaining a number of iterators together,
 the `for_each` version is sometimes clearer. Consider this:
 
 ```rust