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>

Upstream: http://www.nongnu.org/oath-toolkit/index.html

Signed-off-by: Fam Zheng <fam@euphon.net>

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v2: Address comments of yousong and hnyman.