Reserving 'enumeration' keyword in parser

[John W. Eaton]

On 29-Sep-2011, Rik wrote:

| Since the hood of the parser has been opened up recently to add the keyword
| 'parfor', I thought it worthwhile to mention adding the keyword
| 'enumeration'.  The classdef interface for Matlab
| (http://www.mathworks.com/help/techdoc/ref/classdef.html) has a list of
| keywords which Octave mostly already recognizes.  For example, 'iskeyword
| ("events")' returns true.  The only one on the list that Octave doesn't
| recognize is 'enumeration/endenumeration'
| 
| I know we don't have any code for 'enumeration' but it would at least be a
| placeholder and prevent scripts using a reserved keyword that may later be
| implemented.

I checked in the following change.  Like the other classdef stuff,
some syntax is accepted, but nothing is done with it.

http://hg.savannah.gnu.org/hgweb/octave/rev/7861a5fd3479

jwe