Move Win32 event handling to one place

Or technically, two, since the group bridge also does the same loop. We
no longer need special handling for VST2 and VST3 plugins, so we can
simplify things a bit here.

src/wine-host/bridges/common.cpp

@@ -16,5 +16,18 @@
 
 #include "common.h"
 
+#include "../editor.h"
+
 HostBridge::HostBridge(boost::filesystem::path plugin_path)
     : plugin_path(plugin_path) {}
+
+void HostBridge::handle_win32_events() {
+    MSG msg;
+
+    for (int i = 0;
+         i < max_win32_messages && PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE);
+         i++) {
+        TranslateMessage(&msg);
+        DispatchMessage(&msg);
+    }
+}