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>

This commit adds the msmtp-scripts package from SourceForge, which
is a wrapper around msmtp that provides queueing, syslog or file logging,
and a basic SMTP (no auth) server.

Signed-off-by: Daniel Dickinson <lede@daniel.thecshore.com>