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/gpu/gl4/gl4_graphics_system.cc

@@ -292,6 +292,9 @@ void GL4GraphicsSystem::MarkVblank() {
 }
 
 void GL4GraphicsSystem::Swap(xe::ui::UIEvent* e) {
+  if (!command_processor_) {
+    return;
+  }
   // Check for pending swap.
   auto& swap_state = command_processor_->swap_state();
   {