reader: no longer accept %define variable names in quotes

[Akim Demaille]

commit f76a9856cf0bb91924a37b65d7330827bf2c6ab1
Author: Akim Demaille <address@hidden>
Date:   Sat Nov 10 15:52:25 2018 +0100

    reader: no longer accept %define variable names in quotes
    
    It was never documented.
    
    * src/parse-gram.y (variable): Here.

diff --git a/src/parse-gram.y b/src/parse-gram.y
index 74014826..fbaf2eb1 100644
--- a/src/parse-gram.y
+++ b/src/parse-gram.y
@@ -621,15 +621,13 @@ named_ref.opt:
 | BRACKETED_ID   { $$ = named_ref_new ($1, @1); }
 ;
 
+
 /*---------------------.
 | variable and value.  |
 `---------------------*/
 
-/* The STRING form of variable is deprecated and is not M4-friendly.
-   For example, M4 fails for '%define "[" "value"'.  */
 variable:
   ID
-| STRING { $$ = uniqstr_new ($1); }
 ;
 
 /* Some content or empty by default. */