fix Makefile chmod (644)
replace MD5SUM with HASH
add PKG_MIRROR_HASH when PKG_SOURCE_PROTO:=git

(PKG_SOURCE_PROTO:=svn tarballs are not reproducible for now)

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

Pingcheck is a daemon for OpenWRT which checks the online status of individual
network interfaces and makes this information available via UBUS and by
triggering "online" and "offline" scripts.

It is maintained at: https://github.com/br101/pingcheck

Signed-off-by: Bruno Randolf <br1@einfach.org>