Fixed generating chunked response after 46e3542d51b3. If trailers were missing and a chain carrying the last_buf flag had no data in it, then last HTTP/1 chunk was broken. The problem was introduced while implementing HTTP/3 response body generation. The change fixes the issue and reduces diff to the mainline nginx.

make -f misc/GNUmakefile release

the required tools:
*) xsltproc to build CHANGES,
*) xslscript.pl ( http://hg.nginx.org/xslscript ) to build XSLTs
   from XSLScript sources.


make -f misc/GNUmakefile icons

the required tool:
*) netpbm to create Win32 icons from xpm sources.