[O] [BUG] org-special-ctrl-k no longer protects tags

[Matt Lundin]

Since commit e87ebca2a7, setting org-special-ctrl-k to t no longer
protects tags if when pressing C-k (org-kill-line) in the middle of a
headline. The expected behavior is described in the docstring for
org-special-ctrl-k: "When in the middle of the headline text, kill the
headline up to the tags."

Take the following example:

* Headline                              :tag:

If I hit C-k with the cursor on the letter "l" on the example above, I
expect to get this...

* Head                                  :tag:

Instead, I get this...

* Head

I think this is because when (looking-at org-tag-line-re) is called on
line 22840, the cursor is in the middle of the line, whereas
org-tag-line-re expects it to be at the beginning of the line.

Best,
Matt