Events: fixed EPOLLRDHUP with FIONREAD (ticket #2367). When reading exactly rev->available bytes, rev->available might become 0 after FIONREAD usage introduction in efd71d49bde0. On the next call of ngx_readv_chain() on systems with EPOLLRDHUP this resulted in return without any actions, that is, with rev->ready set, and this in turn resulted in no timers set in event pipe, leading to socket leaks. Fix is to reset rev->ready in ngx_readv_chain() when returning due to rev->available being 0 with EPOLLRDHUP, much like it is already done in ngx_unix_recv(). This ensures that if rev->available will become 0, on systems with EPOLLRDHUP support appropriate EPOLLRDHUP-specific handling will happen on the next ngx_readv_chain() call. While here, also synced ngx_readv_chain() to match ngx_unix_recv() and reset rev->ready when returning due to rev->available being 0 with kqueue. This is mostly cosmetic change, as rev->ready is anyway reset when rev->available is set to 0.

/
/ Copyright (C) Igor Sysoev
/ Copyright (C) Nginx, Inc.
/


/  "casa   [%o2] 0x80, %o1, %o0"  and
/  "casxa  [%o2] 0x80, %o1, %o0"  do the following:
/
/       if ([%o2] == %o1) {
/           swap(%o0, [%o2]);
/       } else {
/           %o0 = [%o2];
/       }


/ ngx_atomic_uint_t ngx_casa(ngx_atomic_uint_t set, ngx_atomic_uint_t old,
/      ngx_atomic_t *lock);
/
/ the arguments are passed in the %o0, %o1, %o2
/ the result is returned in the %o0

        .inline ngx_casa,0
        casa    [%o2] 0x80, %o1, %o0
        .end


/ ngx_atomic_uint_t ngx_casxa(ngx_atomic_uint_t set, ngx_atomic_uint_t old,
/      ngx_atomic_t *lock);
/
/ the arguments are passed in the %o0, %o1, %o2
/ the result is returned in the %o0

        .inline ngx_casxa,0
        casxa   [%o2] 0x80, %o1, %o0
        .end