vgrind woe

["James K. Lowden" <jklowden%schemamania.org@localhost>]

http://www.schemamania.org/groff/vgrind/

vgrind isn't working the way I expect it to.  The above PDF shows the
source code alright, but the keywords aren't in boldface and there are
no line numbers.  I'm expecting something more like
http://paco.to/blog/wtf.pdf.  

The invocation is: 

        $ vgrind -f < demo.c  | groff -Tps | ps2pdf - demo.pdf

What am I missing?  

--jkl