multipath-tools: add recipe for git version

Multipath-tools hasn't seen a release in 3 years, so grab latest git.

'kpartx' is subpackaged since that's the tool most people want.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
bbbtester: update to latest git, add -Werror hack

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>