Merge pull request #78 from allanlw/clarify-alias-access-ub

Clarify that breaking the Pointer Aliasing Rules requires an access

Author: steveklabnik

src/behavior-considered-undefined.md

@@ -10,7 +10,7 @@ the guarantee that these issues are never caused by safe code.
   (uninitialized) memory
 * Breaking the [pointer aliasing
   rules](http://llvm.org/docs/LangRef.html#pointer-aliasing-rules)
-  with raw pointers (a subset of the rules used by C)
+  on accesses through raw pointers (a subset of the rules used by C)
 * `&mut T` and `&T` follow LLVM’s scoped [noalias] model, except if the `&T`
   contains an `UnsafeCell<U>`. Unsafe code must not violate these aliasing
   guarantees.