[GSOC] capsicum week6 report

Hi,

this week I've been stabilizing my work a bit more. The implementation
is still rough but "functionnal". I've finished the capability mode by
modifying the sycall path and the syscall table to check if a syscall is
allowed in capability mode and return ECAPMODE if not. I've converted
most of the holdfp calls to check capability rights, but there is still
some calls I must read more carefully to find which rights they need.
I've made the nlookup path return ECAPMODE when doing a non-relative
lookup. For now, the code is not perfect because i can leak information
from outside the sandbox. Indeed, if an early error is returned, I don't
check if the current namecache entry is still in sandbox and return the
error (EEXIST, ENOENT, etc). This is a bug. I've been trying to modify
this behaviour, but for now, it's completely broken.
To test the work, i've ported the capsicum-enabled bzip2 a student has
done for FreeBSD during gsoc :
https://svnweb.freebsd.org/socsvn/soc2013/dpl/head/ . I've run it on a
vkernel, and it can compress and decompress files w/o troubles.

Joris