opkg: fix several package installation bugs

Update to latest Git in order to import the following fixes:

19070b6 unarchive: fix possible segmentation fault in deb_extract()
758527e pkg: forward "provided_by_hand" flag in pkg_merge()
1fdc2ca pkg: mark bit fields in pkg_t unsigned
15fc1ee opkg_cmd: avoid null pointer dereference in opkg_what_depends_conflicts_cmd()
439c89e opkg_cmd: fix endless loop in whatprovides/whatreplaces
0fb3e9f pkg_depends: propagate virtual provided detail flag to providers
793155f pkg_depends: fix unsatisfied dependency installation order
b1dc770 libopkg: fix some overly aggressive line wrapping in pkg_depends.c

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

package/system/opkg/Makefile

@@ -16,9 +16,9 @@ PKG_FLAGS:=essential
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.lede-project.org/project/opkg-lede.git
-PKG_SOURCE_DATE:=2017-02-23
-PKG_SOURCE_VERSION:=f9baf914f8fd0179e575deeebabe463d9f87e850
-PKG_MIRROR_HASH:=ca5df4dc8b2a2dd2c37b1ed2f6a075661c54586f553e8cd056e93021e67c2e83
+PKG_SOURCE_DATE:=2017-03-01
+PKG_SOURCE_VERSION:=19070b6c1a9718bf7ceaa61c48f328cabf1d5ca7
+PKG_MIRROR_HASH:=7fa506c752db01fff47522141e8349603485368ae955315fc41754aec9ecee13
 
 PKG_LICENSE:=GPL-2.0
 PKG_LICENSE_FILES:=COPYING