riched20: ME_StrDup() is no longer used so remove it.

[Huw Davies]

On Tue, Jan 29, 2013 at 07:05:13AM +0100, Francois Gouget wrote:
> ---
>  dlls/riched20/editor.h |    1 -
>  dlls/riched20/string.c |    5 -----
>  2 files changed, 6 deletions(-)

I'm about to send in a patch that uses this again, so please hold off
on this one.

Huw.