[imp] How to add wvHTML to IMP 3.0

[Lars Hecking]

> OK after banging my head a few times (I was in the 
> horde/imp/config/mime_drivers.php)  I get a MSWord icon next to the word 
> attachment but it fails to display the file at all, I get just a blank white 
> browser window.

 All the wv* programs/scripts must be in PATH. In order to not flood my
 web server init scripts with otherwise useless PATH settings, I have,
 for this specific case, modified all wv* scripts to add the path to
 the directory where wvWare and friends live.

 (For maximum convenience, wv* should do this by default, but I had no
  luck contacting the current maintainer and then lost track of the issue.)