Use readv to refill input queue during large reply reads
Submitted by Jamey Sharp @jamey
Assigned to Jamey Sharp @jamey
Description
When XCB reads the header of a response that turns out to be a >4kB reply, it currently does one big read to get the rest of the reply, and then goes back to doing another read to fill the input buffer. For a small optimization, it should instead use readv to request both reads simultaneously.