Linux returns EOPNOTSUPP for non-TCP sockets and ENOPROTOOPT for TCP
sockets, because getsockopt(TCP_FASTOPEN) is not implemented so far.

While there, lower the log level from ALERT to NOTICE to match other
getsockopt() failures.

Signed-off-by: Piotr Sikora <piotr@cloudflare.com>

Init process callbacks are called by ngx_worker_thread(), there is no
need to call them in ngx_single_process_cycle().

Recent Linux versions started to return EOPNOTSUPP to getsockopt() calls
on unix sockets, resulting in log pollution on binary upgrade.  Such errors
are silently ignored now.

This patch fixes incorrect handling of auto redirect in configurations
like:

    location /0  { }
    location /a- { }
    location /a/ { proxy_pass ... }

With previously used sorting, this resulted in the following locations
tree (as "-" is less than "/"):

        "/a-"
    "/0"    "/a/"

and a request to "/a" didn't match "/a/" with auto_redirect, as it
didn't traverse relevant tree node during lookup (it tested "/a-",
then "/0", and then falled back to null location).

To preserve locale use for non-ASCII characters on case-insensetive
systems, libc's tolower() used.

There is nothing to do more when recv() has returned 0,
so we should drop the flag.

Several warnings silenced, notably (ngx_socket_t) -1 is now checked
on socket operations instead of -1, as ngx_socket_t is unsigned on win32
and gcc complains on comparison.

With this patch, it's now possible to compile nginx using mingw gcc,
with options we normally compile on win32.

Several false positive warnings silenced, notably W8012 "Comparing
signed and unsigned" (due to u_short values promoted to int), and
W8072 "Suspicious pointer arithmetic" (due to large type values added
to pointers).

With this patch, it's now again possible to compile nginx using bcc32,
with options we normally compile on win32 minus ipv6 and ssl.