Bit ops/bit masks

Wow, this turned into a saga.

What I'd like to do long term is figure out which of the gcc builtin ops
we could use and get rid of this nonsense, but that's a project for another
day. I did end up using __builtin_popcount, let's hope it actually works.
But by using that I got to NOT use some really awful stuff from the Linux
kernel that I never want to look at again.

This is reasonably good stuff from Linux, otherwise.

I'm turning off the vmx stuff for now because I'm doing some testing with Another
System and the two collide. The vm bits will no longer compile until some rework
is done on them anyway. Sorry.

Signed-off-by: Ronald G. Minnich <rminnich@google.com>