[package] nginx: packaging enhancements

[package] nginx: packaging enhancements
 * add a separate config menu for optionnal modules (not every possible
   module are here; just taken the ones Debian enables). By default they
   are all disabled, so this removes the default dependency on
   libopenssl.
 * correctly listed conffiles
 * enable IPv6 only when CONFIG_IPV6 is set
 * change the default listening adress in nginx.conf when IPv6 is
   enabled so that it listens on [::]

git-svn-id: svn://svn.openwrt.org/openwrt/packages@22807 3c298f89-4303-0410-b956-a3cf2f4a3e73