opkg: update to latest Git head

This update fixes some cosmetical issues and a number of segmentation
faults when parsing lists having Conflicts or Replaces tags.

d217daf libopkg: fix replacelist parsing and writing
9dd9a07 libopkg: fix segmentation fault when traversing conflicts
34571ba libopkg: consider provided packages in pkg_vec_mark_if_matches()
18740e6 opkg_download: print error when fork() fails
e3d7330 libopkg: don't print unresolved dependencies twice

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

package/system/opkg/Makefile

@@ -9,14 +9,14 @@ include $(TOPDIR)/rules.mk
 include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=opkg
-PKG_RELEASE:=3
+PKG_RELEASE:=1
 PKG_FLAGS:=essential
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.openwrt.org/project/opkg-lede.git
-PKG_SOURCE_DATE:=2017-12-07
-PKG_SOURCE_VERSION:=3b417b9f41b4ceb5912d82f867dd5534e5675b5c
-PKG_MIRROR_HASH:=1c9c21e56186345d0034d15051c1d9c5ebb5aa6658d6ae8886d8403207a914a3
+PKG_SOURCE_DATE:=2019-01-18
+PKG_SOURCE_VERSION:=7708a01a084872bbe4c46f36d2da021fdeb10862
+PKG_MIRROR_HASH:=117148ece22e64654264afd869606ef5507edd3dc965ffe000c6b1b1074b3f4a
 
 PKG_LICENSE:=GPL-2.0
 PKG_LICENSE_FILES:=COPYING