Using upper case for variable names in error() strings

[Rik]

1/5/10

In Texinfo variables are marked with the @var{varname} macro.  In the Info
browser displayed with 'help XXX' the macro translates to upper casing the
variable name (VARNAME).  It seems like it would be useful to use upper
case for variable names in strings in calls to error() so that 1) the
warning message would match the documentation and 2) the actual problem is
highlighted to the the user.

I recently tried this for the functions in scripts/statistics/base and it
appeared nice to my eyes.  For example, from center.m,

## @deftypefnx {Function File} {} center (@var{x}, @var{dim})
  and later ...
error ("center: DIM must be an integer and a valid dimension");

What do other people think?  It would be pretty simple to make a Perl
script to extend this to all of Octave's functions.

--Rik