[NTG-context] buffer names in MKII

Dear Hans, something broke backward compatibility in MKII. When using buffers like in \startbuffer[buffername] hello world \stopbuffer the code now creates buffername.tmp instead of \jobname-buffername.tmp. This breaks the gnuplot module in weird ways. I can probably fix it in one way or another, but I'm not sure why the behaviour would change. To fix the vim module? :) :) :) OK, I need to take some time and try to use Aditya's code in the background anyway, but I still wonder if the change was intentional or not. Thanks, Mojca