[RFC] HTTP Timezone - rev4

After considering all feedback, I've changed the TZ information a lot.

The attached draft contains all changes. It is not yet submitted as a draft.

I changed the format of the timezone header to:

client-timezone  =  "Timezone" ":" tzdescr
tzdescr          =  rfctime [ ";" posixtz [ ";" tznames ] ]
rfctime          =  <local time>
posixtz          =  <a POSIX 1003.1 timezone string>
tznames          =  tzname *( "," tzname )
tzname           =  <a timezone string from a timezone database>

There are 3 parts now that contain the current time, the current time offset, 
the posix timezone string and a list of timezone names.

It seems that there is a variety of different needs regarding the client 
timezone. Timezone information can be described in 3 ways:

* Current time offset: This only applies to the current moment.
* POSIX timezone string: This one is able to describe the current year's 
timezone information. Previous or future years may have different DST 
settings.
* Timezone name: This is a name from a timezone database (if available). A 
timezone database is able to hold all past DST changes and some for the 
future.

I also added a section that discusses timezone issues and all rationale behind 
this.

This revision was produced using xml2rfc (previous were written using nroff).

As always, all comments are welcome!