Core: fixed environment variables on exit. Similarly to 6822:c045b4926b2c, environment variables introduced with the "env" directive (and "NGINX_BPF_MAPS" added by QUIC) are now allocated via ngx_alloc(), and explicitly freed by a cleanup handler if no longer used. In collaboration with Sergey Kandaurov.

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.