Document server debugging info block

And the patch. Committed to 7.x.3. Needs backport.

Patch committed for 7.x.2.

Moving versions.

Documentation, which needs to be added to the d.o. docs.

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5.3 Block -- Domain Access Server Information

Provides a block of information related to the current page request. Use this
block to help determine how a server request is being handled by Domain Access.

If you are having trouble with domains not resolving correctly, this block can
help you pinpoint the problem. In particular, note the first two lines of the
output:

  HTTP_HOST request     example.com
  Domain match          TRUE

The first line tells you what HTTP_HOST (i.e. the domain string) was passed by
the server to Drupal. The second line indicates how Domain Access reads that
value.

Possible replies for the 'Domain match' value are:

  TRUE
    Indicates a matching domain record.
  FALSE: Using default domain
    Indicates a non-matching domain, and that Domain Access is using the
    default domain as a fallback.
  ALIAS: Active id #
    Used when Domain Alias is installed. Indicates that the request matched a
    known alias of the active domain.

Below the Domain match line, you will see additional information about the
current $_domain global object.

NOTE: By design, this block is viewable by all users.  However, its content
should only be shown to site developers or during debugging.  You should use
the normal block visiblity settings as appropriate to your site.

The patch for D6, also committed.

Forgot to disable block cache for that. Follow-up for D6, also committed.

Added https://drupal.org/node/1096980