Hi all.

As I mentioned on tech-kern a couple of weeks ago, I was working on a
way to make the `allocsys()' machine independant, since at that time
it was duplicated across most of the ports.

After taking the feedback I received into consideration, I've
committed this code.

The code should compile and run on all the ports (it's a fairly
trivial change), but I've only tested it on the i386.

Also, the method of printing out system memory sizes has been made
consistent, and uses a new kernel function - format_bytes() (which
uses another new function; humanize_number()) to display the info.

(A side effect of this change is that all ports should now support
the BUFCACHE option).