Prefer visual-line-mode to longlines-mode

  Emacs 23 NEWS says visual-line-mode "is a more reliable replacement for
  longlines-mode."
Thanks
Save match data in markdown-check-change-for-wiki-link

  It's used in after-change-functions, which leads to weird bugs when the match
  data changes inside functions that didn't expect that
  (like dabbrev--safe-replace-match).
  Also, set inhibit-point-motion-hooks only once

Signed-off-by: Jason Blevins <jrblevin@sdf.org>
Thanks again
Don't require Common Lisp extensions at run time

Following Lisp Coding Conventins (Coding Conventions(elisp)),
to avoid name conlicts, we should change

    (require 'cl)

to

    (eval-when-compile (require 'cl))

Thanks to Shigeru Fukaya for pointing this out.
Improve markdown-mode-hook docstring

Thanks to Shigeru Fukaya for the more precise description.
Support for setext-style headers in outline-mode

Thanks to Shigeru Fukaya for the patch.
Font locking for fenced code blocks
Add two tab stops to possible indentation positions after list items

Supports list items with pre blocks after the first paragraph:

1. Here is a list item.

       printf("code line\n");
^  ^^  ^

   second paragraph for the list item.

In this case, this patch adds column 7 to the list of indentation
positions, in addition to 0 (the beginning of the line), 3 (the column
where the text of the previous list item begins), and 4 (the first tab
stop).
Reference link insertion
Fix typo in paragraph-fill regexp
Support both forms of aliased wiki links

Introduce a new boolean custom variable, markdown-wiki-link-alias-first.
When set to a non-nil value, markdown-mode will treat aliased wiki links
like [[link text|PageName]].  When set to nil, they will be treated as
[[PageName|link text]].

Note that the default behavior has been changed!  The default behavior
now agrees with GitHub and other wikis which place the link text first.
To reinstate the previous behavior, which agreed with Instiki's behavior,
the new custom variable must be set to nil.
Handle wiki links like GitHub when in gfm-mode

[[Test Test]] and [[test test]] now both link to Test-test.ext.

Thanks to Kevin Porter.
Font lock and insertion and navigation functions for footnotes

Note: the binding for following wiki links has changed from C-c C-f
to C-c C-w.  All footnote related commands are now prefixed by
C-c C-f.
Avoid duplication of header regexes
Add documentation for footnote functions
Properly downcase filenames for wiki links in gfm-mode

Fixes 6bd845e.
Thanks to Kevin Porter.
Added refontify-buffer after calling gfm-mode so that links are highlighted correctly
Make reference link definition regex less greedy

Fixes a bug where reference-style links at the beginning of a line
would be mistaken for reference definitions.
Add markdown-footnote-kill (C-c C-f k)

Thanks to Joost Kremers <joostkremers@fastmail.fm>