Merge pull request #617 from rust-lang-nursery/2015-supports-kleene-question

Rust 2015 supports Kleene ? macro operator

Author: ehuss

src/macros-by-example.md

@@ -33,8 +33,8 @@
 > _MacroRepSep_ :\
 > &nbsp;&nbsp; [_Token_]<sub>_except delimiters and repetition operators_</sub>
 >
-> _MacroRepOp_<sub>2018+</sub> :\
-> &nbsp;&nbsp; `*` | `+` | `?`<sub>2018+</sub>
+> _MacroRepOp_ :\
+> &nbsp;&nbsp; `*` | `+` | `?`
 >
 > _MacroTranscriber_ :\
 > &nbsp;&nbsp; [_DelimTokenTree_]
@@ -181,10 +181,6 @@ compiler knows how to expand them properly:
     illegal because it does not have the same number. This requirement applies
     to every layer of nested repetitions.
 
-> **Edition Differences**: The `?` repetition operator did not exist before the
-> 2018 edition. Prior to the 2018 Edition, `?` was an allowed
-> separator token, rather than a repetition operator.
-
 ## Scoping, Exporting, and Importing
 
 For historical reasons, the scoping of macros by example does not work entirely like