Better organize the filecaps structure, which reduces its size from 32 bytes
to 24 bytes on 64bit archs.
Add process descriptors support to the GENERIC kernel. It is already being
used by the tools in base systems and with sandboxing more and more tools
the usage should only increase.

Submitted by:	Mariusz Zaborski <oshogbo@FreeBSD.org>
Sponsored by:	Google Summer of Code 2013
MFC after:	1 month