klibc_1.5.26: now build against linux-libc-headers

* add install-patch creating symlinks as done by debian
* extra add the mtd headers
* refresh patches (split out prefix.patch)
* recipe is now not machine-specific anymore
* bump INC_PR

Signed-off-by: Andrea Adami <andrea.adami@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>