This allows to detect client connection close with pending data when
the ngx_http_test_reading() request event handler is set.

This allows to detect client connection close with pending data on Linux
while processing upstream.

After 62be77b0608f nginx can return this code.

Reported by Weibin Yao,
http://mailman.nginx.org/pipermail/nginx-devel/2013-April/003607.html.

Additionally, detaching a cleanup chain from a request is a bit more resilent
to various bugs if any.

Casts between pointers and integers produce warnings on size mismatch.  To
silence them, cast to (u)intptr_t should be used.  Prevoiusly, casts to
ngx_(u)int_t were used in some cases, and several ngx_int_t expressions had
no casts.

As of now it's mostly style as ngx_int_t is defined as intptr_t.

On win32, time_t is 64 bits wide by default, and passing an ngx_msec_int_t
argument for %T format specifier doesn't work.  This doesn't manifest itself
on other platforms as time_t and ngx_msec_int_t are usually of the same size.

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.

Precompiled headers are disabled as they lead to internal compiler errors
with long configure lines.  Couple of false positive warnings silenced.
Various win32 typedefs are adjusted to work with Open Watcom C 1.9 headers.

With this patch, it's now again possible to compile nginx using owc386,
with options we normally compile on win32 minus ipv6 and ssl.