Linux's sendfile() returns 0 when remote has closed connection. Convert it to EPIPE.
Linux's sendfile() returns 0 when remote has closed connection. Convert it
to EPIPE.

--HG--
branch : HEAD

jwm/dovecot-notmuch,dscho/dovecot,jkerihuel/dovecot,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,dscho/dovecot,jwm/dovecot-notmuch,dscho/dovecot,jkerihuel/dovecot,jkerihuel/dovecot,dscho/dovecot,jwm/dovecot-notmuch,dscho/dovecot