virtualbox r0 memory management update [Was: Freeze with 10.0 and VirtualBox {4.1.4|4.1.6|4.1.51r38464}]

Meanwhile, here is the code that I came up with:
http://people.freebsd.org/~avg/vbox/
For your convenience I have uploaded both the new file and its diff against svn
head.  I am testing this on FreeBSD head (r228017), so far no breakage observed.

I would appreciate reviews and testing of this code.  Especially testing with
earlier FreeBSD releases.

Thank you!
-- 
Andriy Gapon