`vallen` is verified to be less than `len`, therefore, it can never
be the case that `vallen >= len + sizeof(rhostname)`.

This PR fixes the check so the `rhostname` array does not overflow.

Reported-by: Github Security Lab <securitylab@github.com>
Signed-off-by: Alvaro Muñoz <pwntester@github.com>

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>