Merge r1840010 from trunk:

On the trunk:

mod_http2: connection IO event handling reworked. Instead of reacting on 
     incoming bytes, the state machine now acts on incoming frames that are 
     affecting it. This reduces state transitions. 


Submitted by: icing
Reviewed by: icing, ylavic, jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1840757 13f79535-47bb-0310-9956-ffa450edef68