Fix #187: handle EINPROGRESS and EALREADY in sendfile driver
Fix #187: handle EINPROGRESS and EALREADY in sendfile driver

Thanks to Maas-Maarten Zeeman for reporting this.

jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws