Have seperate variable on ap_writev to set the number of iovecs passed in

and pass back the number of bytes written. Use ap_iovec_t on the call rather
than struct iovec (I may reverse this tomorrow :-). Whatever we do, the network_io
and file_io calls need to use iovecs consistently, which isn't the case now.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@84642 13f79535-47bb-0310-9956-ffa450edef68