No underscore in FLOWchart module

[Nigel King <king@dircon.co.uk>]

In the FLOWchart module underscore is not allowed which is unfortunate since
underscores are used so often in software. I include MPgraphic test to show
that the problem is not there.

% minimum test file to demonstrate underscore error
\usemodule[chart]
\starttext
$a_b$

\type{c_d}

\startuseMPgraphic{graphicname}
label(btex \type{e_f} etex, origin);
\stopuseMPgraphic
\useMPgraphic{graphicname}

\setupFLOWcharts
    [nx=1,ny=1,
    dx=1.5\bodyfontsize,dy=1\bodyfontsize,
    width=8\bodyfontsize,height=5\bodyfontsize,
    maxwidth=\textwidth]
\startFLOWchart[test]
    \startFLOWcell
        \name    {start}
        \location    {1,1}
        \shape    {node}
        \text    {\type{g_h}}
    \stopFLOWcell
\stopFLOWchart
\FLOWchart[test]
\stoptext

! Extra }, or forgotten $.
\FLOWtext ->\type {g_h}

\doprocessFLOWcellD ...OWshapeheight ] {\FLOWtext
                                                  }}\showFLOWhelp 0 \ifx
\FL...

\startFLOWcell ...essFLOWcellD \FLOWlocation \end
                                                  \let \connection
\doFLOWco...
l.6 ^^I\stopFLOWcell

? <to be read again>
                   _
\FLOWtext ->\type {g_
                     h}
\doprocessFLOWcellD ...OWshapeheight ] {\FLOWtext
                                                  }}\showFLOWhelp 0 \ifx
\FL...

\startFLOWcell ...essFLOWcellD \FLOWlocation \end
                                                  \let \connection
\doFLOWco...
l.6 ^^I\stopFLOWcell

? 

-- 
Nigel