Replace *MD5SUM with *HASH, replace MD5 hashes with SHA256

Signed-off-by: Felix Fietkau <nbd@nbd.name>

Simply disable the build of the "doc" and "tests" directories to speed up the
build and avoid the potential for errors coming from external tools being used
(e.g: source-highlight installed on a non-standard location).

Signed-off-by: Florian Fainelli <florian@openwrt.org>

SVN-Revision: 45713

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 43440

Signed-off-by: Imre Kaloz <kaloz@openwrt.org>

SVN-Revision: 43437