jsonfilter: allow empty paths

Allow path specifications to refer to just '@' or '$' which is useful for
exporting the keys or array indizes of the toplevel object to the shell.

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

package/utils/jsonfilter/Makefile

@@ -1,13 +1,13 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=jsonfilter
-PKG_VERSION:=2014-06-19
+PKG_VERSION:=2016-05-24
 PKG_RELEASE=$(PKG_SOURCE_VERSION)
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(OPENWRT_GIT)/project/jsonpath.git
 PKG_SOURCE_SUBDIR:=$(PKG_NAME)-$(PKG_VERSION)
-PKG_SOURCE_VERSION:=cdc760c58077f44fc40adbbe41e1556a67c1b9a9
+PKG_SOURCE_VERSION:=596f31e7c6e59685d1c04e91ea01b5982c044459
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION)-$(PKG_SOURCE_VERSION).tar.gz
 CMAKE_INSTALL:=1