Add automatic memory manager

[Ryan Gonzalez]

Manually freeing assembled functions is dangerous. It's aggravating to manually manage memory, and it's not exception safe. I propose an automatic function holder. Something like this:

AsmJit::AutoFunc<FunctionType> f{my_assembler.make()};

...

f.call(my_args);

// Function deleted when it goes out of slope

--

Ryan

If anybody ever asks me why I prefer C++ to C, my answer will be simple: "It's becauseslejfp23(@#Q*(E*EIdc-SEGFAULT. Wait, I don't think that was nul-terminated."