Properly scope variable evaluation to the function the traced process is
currently stopped in.

Areas that need improving:

* Code cleanup
* Promote breakpoints back out of thread context
* Fix potential bug in "Next" implementation, when thread contexts
  switch

Fix bug involving detecting whether or not we have stepped into another
function when we plan on return from the function we are currently in.

Once the program detects that we have stepped into another function,
we simply calculate the return address and then set a breakpoint and
continue to that location, avoiding numerous syscalls.

Needs some refactoring and some optimization, but fixes several bugs.

Now that I'm using the step strategy, I put in an optimization where if
stepping into another function, simply find the return address, put a
breakpoint there, and then continue.