Remove nonexistent function declaration

The API function definition for Jim_InitStringRep() has been removed
by the commit:

commit 2e8b9ddb92ed1cea3054ed8180d363c9dcc72dd9
Author: Steve Bennett <steveb@workware.net.au>
Date:   Sat Feb 18 14:47:11 2012 +1000

  Small cleanup/optimisation in object create/dup

Remove the declaration from the headers as well.

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
example.api: Replace string object initialization

The object initialization relies on the API function:
Jim_InitStringRep(), yet this function has been removed
by this commit.

commit 2e8b9ddb92ed1cea3054ed8180d363c9dcc72dd9
Author: Steve Bennett <steveb@workware.net.au>
Date:   Sat Feb 18 14:47:11 2012 +1000

    Small cleanup/optimisation in object create/dup

(BTW, it's not very clean to remove an API function and
not even specify that in the commit message).

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Clean up jim_return.c example

Removes a warning and simplifies through the use of Jim_Length()

Reported-By: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Steve Bennett <steveb@workware.net.au>