[patch] For avoid stap output error message of un-defined variable twice

[Frank Ch. Eigler]

"Zhaolei" <zhaolei@cn.fujitsu.com> writes:

> I tried using un-defined variable in print function as mentioned in CaiFei's 
> mail in Fri, 17 Aug 2007 10:39:07 +0900.
> And I found that error message had been displayed twice.
>[...]

Good catch!  Looking over elaborate.cxx, it seems that all code nearby
should be converted to use the newer duplicate elimination logic found
in session::print_error.  I committed a patch to that effect.  (If you
find other such bugs, a similar approach should work.  There should be
only a few direct references to cerr in the sources.)

- FChE