Merge pull request rust-lang#1149 from pushkine/patch-4

Add undocumented Punctuation token Tilde `~`

Author: ehuss

src/tokens.md

@@ -596,6 +596,7 @@ usages and meanings are defined in the linked pages.
 | `#`    | Pound       | [Attributes]
 | `$`    | Dollar      | [Macros]
 | `?`    | Question    | [Question mark operator][question], [Questionably sized][sized], [Macro Kleene Matcher][macros]
+| `~`    | Tilde       | The tilde operator has been unused since before Rust 1.0, but its token may still be used
 
 ## Delimiters