is still worthwhile.

If file inode was not changed, cached file information was not updated
on retest.  As a result stale information might be cached forever if file
attributes was changed and/or file was extended.

This fix also makes obsolete r4077 change of is_directio flag handling,
since this flag is updated together with other file information.

On file retest open_file_cache lost is_directio if file wasn't changed.
This caused unaligned operations under Linux to fail with EINVAL.
It wasn't noticeable with AIO though, as errors wasn't properly logged.

NetBSD 5.0+ has SO_ACCEPTFILTER support merged from FreeBSD, and having
accept filter check in FreeBSD-specific ngx_freebsd_config.h prevents it
from being used on NetBSD.  Therefore move the check into configure (and
do the same for Linux-specific TCP_DEFER_ACCEPT, just to be in line).

Previously only first log level was required to be correct, while error_log
directive in fact accepts list of levels (e.g. one may specify "error_log ...
debug_core debug_http;").  This resulted in (avoidable) wierd behaviour on
missing semicolon after error_log directive, e.g.

    error_log /path/to/log info
    index index.php;

silently skipped index directive and it's arguments (trying to interpret
them as log levels without checking to be correct).

enabled in any server. The previous r1033 does not help when unused zone
becomes used after reconfiguration, so it is backed out.

The initial thought was to make SSL modules independed from SSL implementation
and to keep OpenSSL code dependance as much as in separate files.