Allow rst links to wrap over multiple lines

[mgalloy]

Currently, a link in an IDldoc code header can't span more than one line. A link to a long URL therefore might exceed 80 characters, in which case the world would end. It would be nice to be able to split the link over more than one line, e.g.,

; Ultimate IDL knowledge can be gained from `michaelgalloy.com
; <http://michaelgalloy.com>`.

I think this would make the header more readable.