replace talloc with ralloc

Replace all talloc usage with ralloc from Mesa project. Ralloc is a
lightweight replacement for talloc under MIT license. This removes
the GPLv3 requirement and allows using MAND again under MPL 2.0 or
GPLv2.

This depends on https://github.com/opencpe/openwrt-packages/pull/4

Signed-off-by: Jonas Gorski <jogo@openwrt.org>