Matlab-compatible string class

[John W. Eaton]

With this change:

  http://hg.savannah.gnu.org/hgweb/octave/rev/0b65949870e3

we are beginning to handle the existence of the Matlab string class that 
is now created in Matlab when double quoted strings are used.  I expect 
that it will not be too long before users will expect full compatibility 
in this area.  But I'm not sure how we will transition from Octave's 
current behavior for double-quoted string constants to the one now used 
by Matlab.  For example, in  Octave "foo\n" is a 4-element character 
array containing 'f', 'o', 'o', and a linefeed character.  In Matlab it 
is a string object, but it also contains 5 characters, 'f', 'o', 'o', 
'\', and 'n'.  I'm sure there are other differences, but this is sure to 
cause some trouble.  I don't see a smooth transition path.  Does anyone 
have any ideas about what to do?

jwe