texi2dvi: hard space in a macro

[Kevin Ryde]

In an i386 Debian packaged texinfo 4.0 and tetex-bin 1.0.7, and
texinfo.tex 2001-05-24.08, the foo.texi below processed with

        texi2dvi foo.texi

produces something like,

        Here is a space @endinput blah blah

the "@endinput" being very much unintended.

Perhaps this is only when "@ " is the last thing in a macro, since it
seems to work at the start or in the middle.

foo.texi