igmpproxy: add missing include

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

Backport of r41957

git-svn-id: svn://svn.openwrt.org/openwrt/branches/barrier_breaker@41979 3c298f89-4303-0410-b956-a3cf2f4a3e73

package/network/services/igmpproxy/patches/010-missing_include.patch

+--- a/src/os-linux.h
++++ b/src/os-linux.h
+@@ -3,6 +3,7 @@
+ #include <linux/mroute.h>
+ #include <netinet/ip.h>
+ #include <netinet/igmp.h>
++#include <sys/types.h>
+ 
+ static inline u_short ip_data_len(const struct ip *ip)
+ {