[NTG-context] Forbidden things in bookmarks

[nico]

Hello,

The heading bookmarks don't accept some macros, like \copyright.

In latex there's a handy feature that allows to define the text to put in  
the TOC and the text in the heading itself, like \chapter[Title in the  
TOC]{Actual Title in the doc}. Is it possible to do it in context? If not,  
maybe it could be an interesting feature to add.

Example crashing if \placebookmarks used:

\setupcolors[state=start]
\setupinteraction[state=start]

% also generate pdf bookmarks
\placebookmarks
         [chapter,section,subsection]

\startfrontmatter
\completecontent
\stopfrontmatter

\startbodymatter
\starttext
\chapter{A \copyright}
a a a
\stopbodymatter
\stoptext

Regards,
BG