* This allows the native syntax `for f in Stream:iter() do ... end` without using lambda
  functions.
  Also you can use `break` and `return` statements.
* On the other hand we cannot exploit the extended xpcall() semantics and had to introduce
  another lambda in Stream:play().
* In general the number of function calls per tick stays the same.
  Stream:gtick() itself could be used as an iterator, but Stream:iter() adds checking for CTRL+C,
  resetting of the sample cache and binding functions.

* Just like the original LuaJIT interpreter, this will use a hook to automatically
  raise an error from Lua code.
* Unfortunately, as long as Jit compilation is enabled, this cannot reliably work.
  Therefore we still set an `interrupted` flag that must be
  polled from tight loops.
* Instead of polling via applause_push_sample() which gave interruption-support only
  to Stream:play(), we now have a separate checkint() function.
* checkint() should be manually added to all tight loops.
* Stream:foreach() and everthing based on it is now also supporting interruptions
  (via checkint()).
* This internally works via applause_is_interrupted().
  A C function was exposed only because LuaJIT does not support volatile-qualifiers and
  would optimize away reads to the interrupted-flag.
  As a side effect, we can also reset the hook.
* Flags set in signal handlers should be `volatile`.
* Added likely() and unlikely() macros to C code.
* Updated sample.ipynb Jupyter notebook: Everything important is now supported, albeit
  requiring custom ILua patches.

* This is at the very least cool to have and will be worthwile to write about in the dissertation.
* Added ilua-wrapper.sh script which can be used as the ILua interpreter and/or can be symlinked to `lua` in PATH,
  so ILua will pick up Applause even in Notebooks without any additional tweaks.