Merge r1671918, r1673113 from trunk:

allow time to first byte (of response headers)
to be logged by mod_logio.  

mod_logio was just a conveninent place to do this 
w/o writing a new filter or complicating an existing 
important one.



Use 'unsigned int' in bitfield


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1673904 13f79535-47bb-0310-9956-ffa450edef68