* Remove tracepoint.py

The `Tracepoint` class which implements the necessary
support for the tracepoint kprobe-based hack is no
longer needed and can be removed.

* argdist: Native tracepoint support

This commit migrates argdist to use the native bcc/BPF
tracepoint support instead of the hackish kprobe-
based approach. The resulting programs are cleaner
and likely more efficient.

As a result of this change, there is a slight API
change in how argdist is used with tracepoints. To
access fields from the tracepoint structure, the user
is expected to use `args->field` directly. This
leverages most of the built-in bcc support for
generating the tracepoint probe function.

* trace: Native tracepoint support

This commit migrates trace to use the native bcc/BPF
tracepoint support instead of the hackish kprobe-
based approach. The resulting programs are cleaner
and likely more efficient.

As with argdist, users are now expected to use the
`args` structure pointer to access the tracepoint's
arguments.

For example:

```
trace 't:irq:irq_handler_entry (args->irq != 27) "irq %d", args->irq'
```