can not upgrade to math/gnuplot 4.2.2

[Andriy Gapon]

Upgrade to math/gnuplot 4.2.2 fails at installation stage in generating
.info from .texi:

$ make install
...
install  -o root -g wheel -m 444 gnuplot.gih
/usr/local/share/gnuplot/4.2/gnuplot.gih
/bin/sh /usr/ports/math/gnuplot/work/gnuplot-4.2.2/missing --run
makeinfo -I. ./gnuplot.texi --no-split --output=gnuplot.info
./gnuplot.texi:283: Multiline command @example used improperly.
./gnuplot.texi:308: Multiline command @example used improperly.
./gnuplot.texi:335: Multiline command @example used improperly.
./gnuplot.texi:344: Multiline command @example used improperly.
./gnuplot.texi:10191: Multiline command @example used improperly.
./gnuplot.texi:10238: Multiline command @example used improperly.
./gnuplot.texi:10245: Multiline command @example used improperly.
./gnuplot.texi:10943: Multiline command @example used improperly.
./gnuplot.texi:19640: Multiline command @example used improperly.
./gnuplot.texi:19649: Multiline command @example used improperly.
./gnuplot.texi:19663: Multiline command @example used improperly.
makeinfo: Removing output file `gnuplot.info' due to errors; use --force
to preserve.
*** Error code 1

Stop in /usr/ports/math/gnuplot/work/gnuplot-4.2.2/docs.
...

Not sure exactly why this happens. I think that gnuplot.texi file is
also a generated file and it is generated with a help of (x)emacs and
some lisp script. But I am not sure where the source of the problem is.
BTW, I've tried modifying Makefile to use both makeinfo from base system
and makeinfo from texinfo-4.8_5 and the errors are precisely the same.

I see that some time in the past generation of .texi file was disabled
and then it was re-enabled again but I am not sure if that is related.
BTW, all places that makeinfo complains about look like the following:
uref{http://www.gnuplot.info/demo/simple.html,
@example
          http://www.gnuplot.info/demo/simple.html
@end example

}
That is @example- at end within uref{}, but I am not familiar with texi syntax.

My system:
FreeBSD 6.2-RELEASE-p6 amd64
xemacs-devel-mule-21.5.b28_2
math/gnuplot 4.2.2
$ make showconfig
===> The following configuration options are available for gnuplot-4.2.2:
     GD=on "Enable GD support"
     GRIDBOX=off "Use the gridbox optimization for hidden3d"
     PDF=on "Enable PDF support"
     PLOT=on "Enable plot support"
     THINSPLINES=off "Enable thin plate splines for grids in dgrid3d"
     WX=on "Enable WX support"
===> Use 'make config' to modify these settings

-- 
Andriy Gapon