better "pr" with gdb-6.4

[Dan Nicolaescu <dann@ics.uci.edu>]

Using "pr" when debugging is a bit inconvenient because one has to do:

p VARIABLE
pr 

Instead it would be nicer to just do:
pr VARIABLE

Well, with gdb-6.4 this is possible, thanks to a new variable ($argc)
that holds the number of arguments passed to a command. "pr" can now
be written like this to support both versions shown above:

define pr
  if ($argc == 0)
     set debug_print ($)
  elif ($argc == 1)
     set debug_print ($arg0)
  end
end

Processing even more arguments can be done by adding more "elif"
  elif ($argc == 2)
     set debug_print ($arg0)
     set debug_print ($arg1)

Unfortunately AFAIK it is not possible to do it in a simpler way
(there's no equivalent of Bourne shell's "shift" and the positional
arguments cannot be accessed through a variable that can be
incremented in a loop).

I don't know enough about autoconf to integrate the above in the build
system, but maybe some of you might be useful as a local hack until
properly integrated in emacs....

        --dan