-HEAD configure issue with libedit on linux

There seem to be a number of issues with our libedit support.
One of them is that we fail to build on Linux (at least on Debian
Etch/4.0 x86_64 and i386) if libedit-dev is installed but not
libreadline5-dev.

The problem is that in that configuration ./configure seems to think
that there is a working strlcpy available due to the fact that it
includes -ledit in the relevant configure test which seems to provide
strlcpy :-(
This results in a compile time failure as can be seen on:

http://www.pgbuildfarm.org/cgi-bin/show_log.pl?nm=Shad&dt=2006-11-29%2019:39:31

It looks like emu is the only box on the buildfarm building with
--with-libedit-preferred which might explain why we have not noticed
that earlier.

Stefan