After event is delivered from the kernel its further processing is blocked.
Non-ready TSL I/O operation should mark connection I/O state as not ready
to unblock events and to allow their further processing. Otherwise
the connection hangs.

According to CGI/1.1 RFC 3875:

   The server MUST set this variable; if the Script-URI does not include a
   query component, the QUERY_STRING MUST be defined as an empty string ("").

Python's PEP 333(3) allows omitting it in WSGI interface; PHP docs force no
requirements; PSGI and Rack specifications require it even if empty.

When nginx proxies requests over FastCGI, it always provides QUERY_STRING.
and some PHP apps have been observed to fail if it is missing (see issue
#201 on GitHub).

A drawback of this change (besides a small overhead) is that there will be
no easy way to tell a missing query string from an empty one (i.e. requests
with or without the "?" character); yet, it's negligible compared to the
possible benefits of wider application compatibility.

This closes #226 issue on GitHub.

When idle timeout occurs at the same time as a request comes in,
the timer handler closes connection while the read event triggers
request processing, and this eventually leads to segmentation fault.

As far as I understand, this field is important to control the number of
buffers send in a single write attempt.  Furthermore, having uninitialized
field is always bad.

This closes #204 issue on GitHub.
Thanks to 洪志道 (Hong Zhi Dao).

This patch contains various logging improvements and bugfixes found
during Java module development.

This message produces too many noise in log and complicates analysis.

Fragmented message non-mmap buffer chain not freed nor reused before
this fix.

This closes #206 on GitHub.
Thanks to 洪志道 (Hong Zhi Dao).