Previously, a chunk of spaces larger than NGX_CONF_BUFFER (4096 bytes)
resulted in the "too long parameter" error during parsing such a
configuration.  This was because the code only set start and start_line
on non-whitespace characters, and hence adjacent whitespace characters
were preserved when reading additional data from the configuration file.
Fix is to always move start and start_line if the last character was
a space.

This fixes wrong permissions and file time after cross-device MOVE
in the DAV module (ticket #1577).  Broken in 8101d9101ed8 (0.8.9) when
cross-device copying was introduced in ngx_ext_rename_file().

With this change, ngx_copy_file() always calls ngx_set_file_time(),
either with the time provided, or with the time from the original file.
This is considered acceptable given that copying the file is costly anyway,
and optimizing cases when we do not need to preserve time will require
interface changes.

Previously, ngx_open_file(NGX_FILE_CREATE_OR_OPEN) was used, resulting
in destination file being partially rewritten if exists.  Notably,
this affected WebDAV COPY command (ticket #1576).

Previously, listenings sockets were not cloned if the worker_processes
directive was specified after "listen ... reuseport".

This also simplifies upcoming configuration check on the number
of worker connections, as it needs to know the number of listening
sockets before cloning.

Errors when sending UDP datagrams can happen, e.g., when local IP address
changes (see fa0e093b64d7), or an unavailable DNS server on the LAN can cause
send() to fail with EHOSTDOWN on BSD systems.  If this happens during
initial query, retry sending immediately, to a different DNS server when
possible.  If this is not enough, allow normal resend to happen by ignoring
the return code of the second ngx_resolver_send_query() call, much like we
do in ngx_resolver_resend().