Multiple improvements and bug fixes.

* Improve indentation extraction.
* Skip problematic References in this style:
 # References:
 #
 # Date: Tue, 1 Oct 2002 02:07:29 -0400
 # From:"Russ" <Russ.Cooper@RC.ON.CA>
 # Subject: Alert:New worms, be aware of internal infection possibilities
 # To:NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM

* Extract same-line References.
* Better detection of tail of description references.
* Remove extra inserted new-line after references extraction.
* Merge joins for script_xref indent.
* Add omitted indent for non-end of description References case.