* Refactor read/write hooks
* add PC to the callbacks
* simplify code, merge common code
* remove useless tcg frees
* use tcg_constant_tl as much as possible, removing most #if in libafl code.
* get rid of as many extern / function definition in QEMU codebase.
* mostly moved cpu / gdb related code.
* move qemu snapshot code in dedicated files.
