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>

Change occurences of `sys/unistd.h` to the standard `unistd.h` include.
Fixes build against musl.

Also refresh existing patch since it applied with fuzz.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

Signed-off-by: Luka Perkov <luka@openwrt.org>

Signed-off-by: Luka Perkov <luka@openwrt.org>