Load plugins with RTLD_GLOBAL, fixes Lua library exports
plugin.c: don't assume post_init callback to exist
relicense to ISC Signed-off-by: Felix Fietkau <nbd@openwrt.org>
add plugin op for uh_chunk_printf
add ubus support
export uh_http_header to plugins
export uh_request_done to plugins
add lua plugin support