uhttpd: update to latest version, fixes compile error with latest libubox

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36338 3c298f89-4303-0410-b956-a3cf2f4a3e73
Merge branch 'master' of git://nbd.name/openwrt into wbm2013