Require one or more spaces (+) between keyword and headline

* org.el (org-scan-tags): Require one or more spaces (+) between
keyword and headline.

Otherwise the re will match a line like:

* TODO@ Foobar

And assumes the @ to be part of the headline.

This fixes a glitch reported by Simon Thum in
<4F53DEF7.8080604@gmx.de>.

> Hi all,
>
> I have found some irritating behaviour, potentially a bug. I have a
> block agenda which goes like:
>
> tags-todo "@home&TODO=\"TODO\"
>
> and it displays a certain org line that reads
>
> **** TODO_ state triggers
>
> Which is just a heading for dealing with TODO state triggers, and I
> appended the _ as I don't want it to be a TODO.
>
> For example, the global TODO list and syntax highlighting does not
> consider it a todo, but C-c a m TODO="TODO" does. TODO="T" does not,
> so it's not very grave.
>
> Most likely, it's simply an inconsistency arising from not having a
> real parser. I just wanted to report it here so it may get fixed.

lisp/org.el

@@ -12785,7 +12785,7 @@ headlines matching this string."
 		     " *\\(\\<\\("
 		     (mapconcat 'regexp-quote org-todo-keywords-1 "\\|")
 		     (org-re
-		      "\\>\\)\\)? *\\(.*?\\)\\(:[[:alnum:]_@#%:]+:\\)?[ \t]*$")))
+		      "\\>\\)\\)? +\\(.*?\\)\\(:[[:alnum:]_@#%:]+:\\)?[ \t]*$")))
 	 (props (list 'face 'default
 		      'done-face 'org-agenda-done
 		      'undone-face 'default