Update www/php-http to 2.5.6.

2.5.6
* Fix php-bug #71719: Buffer overflow in HTTP url parsing
  functions
* Fix gh-issue #28: Possible null pointer dereference
  in php_http_url_mod()
* Fix gh-issue #22: Fix PHP5 config.w32
* Fix gh-issue #20: setSslOptions notice with curl 7.43

2.5.5
* Fixed gh-issue #16: No Content-Length header with empty
  POST requests

2.5.3
* Fixed gh-issue #12: crash on bad url passed
  to http\Message::setRequestUrl()
* The URL parser now fails on empty labels

2.5.2
* Fixed regression with HEAD requests always warning about
  a partial file transfer
+ Added "path_as_is" request option (libcurl >= 7.42)

(fhajny)