[Rd] Platform() used in tkfilefind.X although now deprecated (PR#2316)

[stephen@cogsci.ed.ac.uk]

> library(tcltk)
> demo(tkfilefind)
[then select a file]
[1] "./NEWS"
Warning message: 
`Platform' is deprecated.
Use `.Platform' instead.
See ?Deprecated. 

See R/library/tcltk/demo/tkfilefind.R, line 32.  (Also present in
latest r-devel).

> version
         _                
platform i686-pc-linux-gnu
arch     i686             
os       linux-gnu        
system   i686, linux-gnu  
status                    
major    1                
minor    6.1              
year     2002             
month    11               
day      01               
language R          

Stephen