hide help string

[Peter Johansson]

Hello,

I wonder if it is possible to have an AC_ARG_WITH with no help output. 
The reason I want something like that is because I wanna deprecate my 
`--with-foo' option and I would prefer if I could hide it and yet let 
configure react to it as before.

I tried AC_ARG_WITH with an empty second argument, but that resulted in 
an empty line in the help output which I would prefer to get rid of (if 
possible). Does anyone know any trick how that could be accomplished?

Thanks,
Peter