ftrace: port to the new ring_buffer

These patches are against linux-tip.

The first is just a fix in the wakeup selftest.

The next is a port of the Unified tracer buffer to linux-tip and some updates.

After that is the ftrace port to use the ring buffer, followed by some
more enhancements to ftrace because of the new variable length
buffer.

I tried a few configurations and tried to test all the different ftrace
tracers, but I'm sure there may be some bugs still to work out. I worked
out all those that I found.

But, with the ring_buffer I can envision several ways to clean up
ftrace and to make adding new tracers cleaner.

I'm also thinking about making a way that each tracer can allocate
its own buffer, and allow for more than one tracer to be running
at the same time! (only with different buffers).

-- Steve