Replace obsolete outline commands with their newer versions
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Authored-by: Ramon Diaz-Uriarte (@rdiaz02)

This is no longer necessary, since we are dropping support for Emacs
24.3

Relates to: #26

The correct possessive with it is "its", not "it's".

Closes: politza#689

- Remove :group arguments from `defcustom` declarations
  - `defcustom` picks up `defgroup` names from the same file, so
    specifying the group is not necessary
- Ensure that all function-names are properly quoted using #'
- Add an explicit header-option setting lexical-binding to t
- Ensure that cl-check-type uses `satisfies` for filenames
- Replace all `defadvice` with `advice-add`
- Replace `(list ...)` patterns with `\`(...)` patterns

Fixes: #62
Fixes: #32
Partially Fixes: #24

This removes the positial arguemnt triplet from the define-minor-mode
calls, because they are obsolete since Emacs<21. See the following
paragraph in the help section of define-minor-mode.

For backward compatibility with the Emacs<21 calling convention, the
keywords of define-minor-mode can also be preceded by the obsolete
triplet INIT-VALUE LIGHTER KEYMAP.

This commit gives the user the option to disable the action of
`fill-column` (or customize it to whatever they want) in pdf-outline
buffers. This is useful because outlines frequently contain long
lines, and breaking up the lines destroys the formatting and integrity
of the outline.

Closes politza/pdf-tools#602, politza/pdf-tools#593