Fix more broken links.

Sorry, missed one in my last commit.  Also, #380 recently removed the link, but
not the actual entry.

Author: ehuss

src/keywords.md

@@ -106,7 +106,7 @@ is possible to declare a variable or method with the name `union`.
 [loop labels]: expressions/loop-expr.html#loop-labels
 [Macros]: macros.html
 [attributes]: attributes.html
-[Macro placholders]: macros-by-example.html
+[Macro placeholders]: macros-by-example.html
 [Crates]: crates-and-source-files.html
 [union]: items/unions.html
 [variants]: items/enumerations.html

src/undocumented.md

@@ -13,7 +13,6 @@ to shrink!
   in [Conditional compilation]
 - [`dllimport`] - one element mentioned but not explained at [FFI attributes]
 - [define `crt_link`]
-- [define `unaligned_access`]
 - `impl Trait`
 
 [`libstd` facade]: https://github.com/rust-lang/rfcs/pull/40