A new debugger.

Lots of bugs/rough edges/etc - issues will be filed.
Old-style debugging still works (just use --emit_source_annotations to get
the helpful movs back and --break_on_instruction will still fire).

src/xenia/app/emulator_window.h

@@ -43,6 +43,7 @@ class EmulatorWindow {
   void CpuTimeScalarReset();
   void CpuTimeScalarSetHalf();
   void CpuTimeScalarSetDouble();
+  void CpuBreakIntoDebugger();
   void GpuTraceFrame();
   void GpuClearCaches();
   void ToggleFullscreen();