makeinfo 4.0 does nit-pick more than 3.12 and produces some warnings
when processing gnus.texi:

fabian@mungo ~/emacs/pgnus/texi$ make makeinfo
makeinfo -o gnus gnus.texi
gnus.texi:10746: warning: unlikely character [ in @var.
gnus.texi:10746: warning: unlikely character [ in @var.
gnus.texi:10746: warning: unlikely character [ in @var.
gnus.texi:10746: warning: unlikely character ] in @var.
gnus.texi:10746: warning: unlikely character ] in @var.
gnus.texi:10746: warning: unlikely character ] in @var.
gnus.texi:11920: warning: @sc argument all uppercase, thus no effect.

I think these can be avoided by the following patch: