Prepare web debugger (#247)

src/windows-emulator/process_context.hpp

@@ -34,6 +34,7 @@ struct process_context
     {
         utils::optional_function<void(handle h, emulator_thread& thr)> on_create_thread{};
         utils::optional_function<void(handle h, emulator_thread& thr)> on_thread_terminated{};
+        utils::optional_function<void()> on_thread_switch{};
     };
 
     struct atom_entry

src/windows-emulator/windows_emulator.cpp

@@ -169,6 +169,7 @@ namespace
         }
 
         thread.apc_alertable = false;
+        win_emu.callbacks.on_thread_switch();
         return true;
     }