#277 Headers with leading CRLF canonicalized incorrectly

[Steve Atkins]

This looks identical to #226, but that's marked closed-fixed.

If a header is wrapped immediately after the field name then it's (relaxed) canonicalized form will have a space between the field name and field value.

e.g.

List-Unsubscribe:
   =?us-ascii?q?long_meaningless_value...

will canonicalize to

list-unsubscribe: =?us-ascii?q?long_meaningless_value...

instead of

list-unsubscribe:=?us-ascii?q?long_meaningless_value...

which causes validation to fail.

The RFC says that any whitespace after the colon should be deleted.

(Clone of Github #39)

[Steve Atkins]

[Dilian Wesselinov Palauzov]

Use the software from the develop branch, https://github.com/trusteddomainproject/OpenDKIM/tree/develop .