nghttpx supports hot deploy feature using signals.  The host deploy in
nghttpx is multi step process.  First send USR2 signal to nghttpx
process.  It will do fork and execute new executable, using same
command-line arguments and environment variables.  At this point, both
current and new processes can accept requests.  To gracefully shutdown
current process, send QUIT signal to current nghttpx process.  When
all existing frontend connections are done, the current process will
exit.  At this point, only new nghttpx process exists and serves
incoming requests.

--no-location-rewrite option disallows location header rewrite on
--http2-bridge, --client and default mode.  This option is useful when
connecting nghttpx proxy with --http2-bridge to backend nghttpx with
http2-proxy mode.

It might be useful to clean the unused stream out to make up the room
for new streams.  On the other hand, proxy should maintain the
connection between upstream client and downstream server and they have
the timeout for their own.  Proxy just reacts to their decision.

This reverts commit cc24b9aa.

This function is no longer necessary because 0x00 concatenation rule
is gone.

libjemalloc as static library requires -pthread flag to link.  Without
that, the check in configure.ac fails with unresolved symbols.

Thanks to Pascal