doc: mention earlier how to disable the generation of location.hh (was: Enhancement request: enabling Variant in C parsers)

[Akim Demaille]

> Le 24 oct. 2018 à 18:14, Victor Khomenko <address@hidden> a écrit :
> 
>  * In Sect 10.1.2 it would be good to mention that location.hh can be 
> suppressed (it's explained only later in the text).

I installed this:

commit 73a822e63610daa613174de19fce25a1304d0f35
Author: Akim Demaille <address@hidden>
Date:   Wed Oct 24 18:57:15 2018 +0200

    doc: mention earlier how to disable the generation of location.hh
    
    Suggested by Victor Khomenko.
    
    * doc/bison.texi (C++ Bison Interface): Here.

diff --git a/doc/bison.texi b/doc/bison.texi
index 91b472b7..f104b486 100644
--- a/doc/bison.texi
+++ b/doc/bison.texi
@@ -10846,10 +10846,11 @@ these two files (@address@hidden and @address@hidden) 
follow the
 same rules as with regular C parsers (@pxref{Invocation}).
 
 @item location.hh
-The definition of the classes @code{position} and @code{location}, used for
-location tracking when enabled.  This file is not generated if user defined
-locations are used, i.e., if the @code{%define} variable
address@hidden is defined.  @xref{C++ Location Values}.
+Generated when both @code{%defines} and @code{%locations} are enabled, this
+file contains the definition of the classes @code{position} and
address@hidden, used for location tracking.  This file is not generated if
address@hidden api.location.file none} is specified, or if user defined
+locations are used.  @xref{C++ Location Values}.
 
 @item position.hh
 @itemx stack.hh