signal processing stability:

*) use sys_errlist[] in signal handler instead
   of non Async-Signal-Safe strerror_r()
*) do not update time in the timer signal handler,
   since localtime_r() is not Async-Signal-Safe function
*) use previously cached GMT offset value to update time from a signal handler
*) change ngx_time_update() interface since there are no notification methods
   those return time
*) introduce ngx_time_sigsafe_update() to update the error log time only
*) change ngx_time_update() interface

various ./configure fixes:

*) use md5/sha1 in OpenSSL only if OpenSSL is used
*) stop ./configure at once on library failure
*) librt must be tested before creating Makefile
   the bug has been introduced in r2817

the bug has been introduced in r2818 and broke
*) SSL modules linking on Solaris 9 and lower,
*) and linking with OpenSSL built from sources on Linux

Solaris 10 has dlopen()/etc. in libc

*) move src/os/.../ngx_types.h's content into src/os/.../ngx_files.h and
   delete src/os/.../ngx_types.h

    *) Feature: nginx now logs the subrequest information to the error log.

    *) Feature: the "proxy_next_upstream", "fastcgi_next_upstream", and
       "memcached_next_upstream" directives support the "off" parameter.

    *) Feature: the "debug_connection" directive supports the CIDR address
       form.

    *) Bugfix: if a response of proxied server or FastCGI server was
       converted from UTF-8 or back, then it may be transferred incomplete.

    *) Bugfix: the $upstream_response_time variable had the time of the
       first request to a backend only.

    *) Bugfix: nginx could not be built on amd64 platform; the bug had
       appeared in 0.3.53.