znc: upgrade to 1.6.0

Upgrade to fix CVE-2014-9403
Remove backport patch
Add CSocket submodule, which split from znc
Add the dependency on icu

Signed-off-by: Roy Li <rongqing.li@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>