wikimedia.vcl: set CP ('Connection Properties') cookie in vcl_deliver
Batching ResourceLoader module requests (that is, loading as many modules as
possible in a single request) is essential for site performance for HTTP 1.x
clients. For SPDY clients, it leads to needless cache invalidation, because
whenever a module is updated, we retrieve a whole bunch of other modules with
it. So, set a CP ('Connection Properties') cookie in vcl_deliver with a value
of 'H2' for SPDY clients (I am looking ahead to HTTP 2.0 replacing SPDY).
The format of the cookie will be !-separated fields, like the current CN
Needs bblack's review, since I think I may have promised him at one point or
another not to do this.