.gitignore: match ncscope.out

Sometimes I got this:

    $ git-status
    {snip}
    # On branch master
    # Untracked files:
    #   (use "git add <file>..." to include in what will be committed)
    #
    #       ncscope.out
    nothing added to commit but untracked files present (use "git add"
to track)

Fix it.

Signed-off-by: Jike Song <albcamus@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>