Fix numerous bigs in the FreeBSD backend

* Correct calculation of CPU time.
* Fix a bug on newer versions of FreeBSD where computing the process map leads
to a tight error loop.
* Add support for the new procstat API to obtain the list of open files and
cwd.
* Use kvm_openfiles instead of kvm_open to better handle error messages.
* Split some modules out into non-suid modules.
* Properly determine the number of CPUs.

https://bugzilla.gnome.org/show_bug.cgi?id=605431

sysdeps/freebsd/nosuid.c

@@ -21,16 +21,8 @@
 
 #include <config.h>
 #include <glibtop.h>
-#include <glibtop/open.h>
 #include <glibtop/close.h>
 
-void
-glibtop_open_s (glibtop *server,
-		const char *program_name,
-		const unsigned long features,
-		const unsigned flags)
-{ }
-
 void
 glibtop_close_s (glibtop *server)
 { }