HTTP/3: fixed parsing encoder insertions with empty header value. When starting processing a new encoder instruction, the header state is not memzero'ed because generally it's burdensome. If the header value is empty, this resulted in inserting a stale value left from the previous instruction. Based on a patch by Zhiyong Sun.

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.