Export "main" symbol for VST2 on Windows

Signed-off-by: falkTX <falktx@falktx.com>

distrho/src/DistrhoPluginVST2.cpp

@@ -1740,4 +1740,13 @@ const AEffect* VSTPluginMain(audioMasterCallback audioMaster)
     return effect;
 }
 
+#if DISTRHO_OS_WINDOWS
+// backwards compat with old hosts
+DISTRHO_PLUGIN_EXPORT const AEffect* main(audioMasterCallback audioMaster);
+DISTRHO_PLUGIN_EXPORT const AEffect* main(audioMasterCallback audioMaster)
+{
+    return VSTPluginMain(audioMaster):
+}
+#endif
+
 // -----------------------------------------------------------------------