libcxx: update to support armv8

Signed-off-by: Reto Achermann <reto.achermann@inf.ethz.ch>

libc: removing newlib, adding BSD libc
posixcompat: moving gettimeofday to libc
harness: adding a simple math test
lwip, lwip2: moving includes to /include, compiling with BSD headers

Signed-off-by: Adam Turowski <adam.turowski@inf.ethz.ch>

Patches 4878a9a through 6b8a570