ITS#3636 more flexible file: URLs in LDIFs

[hyc@symas.com]

Some notes... Most of the forms in the original request have been supported in 
2.3/2.4/HEAD for a long time, I just didn't remember this ITS existed. It has 
some bearing on #5117 as well.

Specifically
	file:/absolute/path
	file:relative/path
	file:simple.name
are allowed (but deprecated) by RFC 3986 and are supported. (RFC1808 and 3986 
expect relative URLs to have no scheme specifier at all. We don't handle that 
case. We also don't handle file://localhost/absolute/path and probably should.)

	file://simple.name
violates RFC3986 and is rejected.

The latest draft spec for FILE URIs has died, and it looks like it was plagued 
with too many strange behaviors to formulate a coherent spec.
http://tools.ietf.org/html/draft-hoffman-file-uri-03
http://offset.skew.org/wiki/URI/File_scheme/Plan_of_action

In the meantime, the libcurl API is a lot more complicated than libfetch. Might 
be nice to have, but it will not be as straightforward...

-- 
   -- Howard Chu
   Chief Architect, Symas Corp.  http://www.symas.com
   Director, Highland Sun        http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP     http://www.openldap.org/project/