Remove memory allocation from logging callback invocation

[automaticp]

Currently, implementation of Binding::log allocates a move-constructed FunctionCall on each invocation and passes a raw pointer to the callback. There are 2 issues with this:

• The interface does not tell the user that they have to delete the allocated object;
• The allocation itself is unnecessary and is forced from the side of the library.

I was personally experiencing memory leaks when setting my own logging callback, until I figured out the first part; the second part just generally impacts performance in real-time scenarios.

This PR changes the callback signature from void(FunctionCall*) to void(FunctionCall&&); implementation of Binding::log now just moves the call further to the callback. The builtin aux logging callback that relied on dynamic allocation is modified to reflect the change.