Change the default ‘C-c w’ and ‘C-c W’ key-bindings

Section 22.2.1 of the Emacs Lisp Manual, “Major Mode Conventions,”
says the following about keys:

    The key sequences bound in a major mode keymap should usually
    start with ‘C-c’, followed by a control character, a digit, or
    ‘{’, ‘}’, ‘<’, ‘>’, ‘:’ or ‘;’.  The other punctuation characters
    are reserved for minor modes, and ordinary letters are reserved
    for users.

Users should be able to safely use a key sequence such as ‘C-c w’
without concern for conflicts with any major mode.  However, Wiki Nav
Mode violates that reservation.  Therefore, this patch changes

    C-c w    ->    C-c C-w
    C-c W    ->    C-c C-W

in order to avoid conflicts with users’ keys.