Fix documentation for key_extras authentication helper parameter
Merge from trunk
Revert rev.13253 - fuba
Fix peerSelectDnsResults() IP address cycling

The local ip variable is the index of the IP address to be used.
Loop counter n is only used to prevent cycling indefinitely and should
not be used to access the array indexes.
Prep for 3.4.3
Fix keepalive handling for non-ranged requests.

Internal keepalive flag was ignored by a mismatched interface between ClientSocketContext::socketState
and writeComplete in the case of non-ranged requests.
Fix r13257 commit
Regression Bug 3769: client_netmask not evaluated since Comm redesign