Merge branch 'ps/http-gssapi-cred-delegation'

In recent versions of cURL, GSSAPI credential delegation is
disabled by default due to CVE-2011-2192; introduce a configuration
to selectively allow enabling this.

* ps/http-gssapi-cred-delegation:
http: control GSSAPI credential delegation

diff --cc Documentation/config.txt
Simple merge

diff --cc http.c
Simple merge