Allow loading VST3 modules

Doesn't actually work yet or do anything, but it compiles and it runs.

src/wine-host/bridges/vst3.h

@@ -15,3 +15,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 #pragma once
+
+#include <string>
+
+void justdewit(const std::string& path);