BUG/MINOR: http-htx: Normalized absolute URIs with an empty port

BUG/MINOR: http-htx: Normalized absolute URIs with an empty port

Thanks to the previous commit ("MINOR: http: Considere empty ports as valid
default ports"), empty ports are now considered as valid default ports. Thus,
absolute URIs with empty port should be normalized.

So now, the following URIs are normalized:

 http://example.com:/  --> http://example.com/
 https://example.com:/ --> https://example.com/

This patch depend on:

   * MINOR: h1: Consider empty port as invalid in authority for CONNECT
   * MINOR: http: Considere empty ports as valid default ports

It is a bug regarding the RFC3986. Technically, I may be backported as far
as 2.4. However, this must be discussed first. If backported, the commits
above must be backported too.