[Rd] Rgui open script file selection filter wish

[Jonathan Swinton]

When using the File/Open Script.. dialogue on Windows, the list of filters 
offered is

 R files (*.R)
 S files (*.q,*.ssc,*.S)
 All files (*.*)

I wish that an additional filter be offered as
 Sweave files (*.Rnw,*.Snw)

I find that the Rgui script editor is adequate for most of my R development
and tend to edit *.Rnw files there. 

               _                           
platform       i386-pc-mingw32             
arch           i386                        
os             mingw32                     
system         i386, mingw32               
status                                     
major          2                           
minor          5.0                         
year           2007                        
month          04                          
day            23                          
svn rev        41293                       
language       R                           
version.string R version 2.5.0 (2007-04-23)