Merge of r4654, r4672, r4684, r4685, r4692: resolver changes. *) Resolver: fixed format specification. Patch by Yichun Zhang (agentzh). *) Support for IPv6 literals and an optional port in resolver. *) Fixed crash in ngx_resolver_cleanup_tree(). If sending a DNS request fails with an error (e.g., when mistakenly trying to send it to a local IP broadcast), such a request is not deleted if there are clients waiting on it. However, it was still erroneously removed from the queue. Later ngx_resolver_cleanup_tree() attempted to remove it from the queue again that resulted in a NULL pointer dereference. *) When "resolver" is configured with a domain name, only the first resolved address was used. Now all addresses will be used. *) Fixed segfault with poll and resolver used. Poll event method needs ngx_cycle->files to work, and use of ngx_exit_cycle without files set caused null pointer dereference in resolver's cleanup on udp socket close.

/
/ 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