The code failed to ensure that "s" is within the buffer passed for
parsing when checking for "ms", and this resulted in unexpected errors when
parsing non-null-terminated strings with trailing "m".  The bug manifested
itself when the expires directive was used with variables.

Found by Roman Arutyunyan.

No functional changes.

    *) Change: the "add_header" directive adds the string to 204, 301, and
       302 responses.

    *) Feature: the "server" directive in the "upstream" context supports
       the "weight" parameter.

    *) Feature: the "server_name" directive supports the "*" wildcard.

    *) Feature: nginx supports the request body size more than 2G.

    *) Bugfix: if a client was successfully authorized using "satisfy_any
       on", then anyway the message "access forbidden by rule" was written
       in the log.

    *) Bugfix: the "PUT" method may erroneously not create a file and
       return the 409 code.

    *) Bugfix: if the IMAP/POP3 backend returned an error, then nginx
       continued proxying anyway.