[Rd] no traceback in R-patched

[Roger D. Peng]

Has something changed with traceback's in R-patched?  When I running the 
examples for ?traceback, I get

>      foo <- function(x) { print(1); bar(2) }
>      bar <- function(x) { x + a.variable.which.does.not.exist }
>     foo(2) # gives a strange error
[1] 1
Error in bar(2) : Object "a.variable.which.does.not.exist" not found
>  traceback()
No traceback available
>

It seems the .Traceback variable is never created.

>  version
         _               
platform i686-pc-linux-gnu
arch     i686            
os       linux-gnu       
system   i686, linux-gnu 
status   alpha           
major    1               
minor    8.1             
year     2003            
month    10              
day      28              
language R               

-roger