add RunEternally() & remove unused `#include <iostream>` & remove `using namespace std; & move macros & member initialization into mos6502.cpp

[ghost]

1. add RunEternally() to eliminate the worry that the emulation may stop on exhaustion of cycles. this is useful when emulating a program with a dead loop. e.g. WOZ Monitor.
2. remove unused #include <iostream> & remove using namespace std; it's never used, and it's dangerous to write using namespaces in header files.
3. move macros & member initialization into mos6502.cpp. so macros wont conflict with other headers in a real project. member initialization referenced to a one of the macros, and thus might as well move member initialization to mos6502.cpp.