* Fix instruction-selection dependent functionality.
* Remove odd instruction position jumps in add/remove breakpoint.
* Make PC fixate at 1/3 of the frame because knowing future instructions is more important than knowing the previous.
* Remove m_current_choice, it's not correct to rely on thread name entry. In extreme corner cases a newly thread can be created, old destroyed with the same entry name. (reoccuring LV2 SPU/PPU ID)
* Remove m_no_thread_selected, can be easily replaced with std::weak_ptr expired() function and is more accurate this way.
* In HandleBreakpointRequest: only remove breakpoint on valid PPU thread and not any thread! also fix potential nullptr deref if thread has recently been destroyed.
