libubox: update to the latest version, adds a few utility functions

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

package/libs/libubox/Makefile

@@ -1,13 +1,13 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libubox
-PKG_VERSION:=2016-07-04
+PKG_VERSION:=2016-07-29
 PKG_RELEASE=$(PKG_SOURCE_VERSION)
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(LEDE_GIT)/project/libubox.git
 PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)
-PKG_SOURCE_VERSION:=d3fa561e5abcc88e02eb289c24d0b1d4d05adb54
+PKG_SOURCE_VERSION:=290c64ef5b5c3e75be851594f269d6a9568e64e5
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION)-$(PKG_SOURCE_VERSION).tar.gz
 PKG_MIRROR_MD5SUM:=
 CMAKE_INSTALL:=1