Merge pull request rust-lang#201 from yellow-apple/patch-1

enum representation in C is not undefined but implementation-defined

Author: Havvy

src/attributes.md

@@ -136,8 +136,8 @@ On `enum`s:
   representation. Takes one argument, which is the primitive
   type this enum should be represented for, or `C`, which specifies that it
   should be the default `enum` size of the C ABI for that platform. Note that
-  enum representation in C is undefined, and this may be incorrect when the C
-  code is compiled with certain flags.
+  enum representation in C is implementation-defined, and may not be compatible
+  when the C code is compiled with certain flags.
 
 On `struct`s:
 
@@ -416,4 +416,4 @@ You can implement `derive` for your own type through [procedural macros].
 
 [Doc comments]: comments.html#doc-comments
 [The Rustdoc Book]: ../rustdoc/the-doc-attribute.html
-[procedural macros]: procedural-macros.html
+[procedural macros]: procedural-macros.html