Fix a memory leak in the loonix waterbox interop code that's never been used before ever

BizHawk.Common/BizInvoke/CallingConventionAdapter.cs

@@ -155,6 +155,16 @@ namespace BizHawk.Common.BizInvoke
 				throw new InvalidOperationException("Out of Thunk memory");
 			}
 
+			private int FindUsedIndex(object o)
+			{
+				for (int i = 0; i < _refs.Length; i++)
+				{
+					if (_refs[i] == o)
+						return i;
+				}
+				return -1;
+			}
+
 			private static void VerifyParameter(Type type)
 			{
 				if (type == typeof(float) || type == typeof(double))
@@ -201,10 +211,23 @@ namespace BizHawk.Common.BizInvoke
 			}
 
 			public IntPtr GetFunctionPointerForDelegate(Delegate d)
+			{
+				// for this call only, the expectation is that it can be called multiple times
+				// on the same delegate and not leak extra memory, so the result has to be cached
+				lock (_sync)
+				{
+					var index = FindUsedIndex(d);
+					if (index != -1)
+					{
+						return GetThunkAddress(index);
+					}
+					else
 					{
 						return GetArrivalFunctionPointer(
 							Marshal.GetFunctionPointerForDelegate(d), new ParameterInfo(d.GetType()), d);
 					}
+				}
+			}
 
 			public IntPtr GetArrivalFunctionPointer(IntPtr p, ParameterInfo pp, object lifetime)
 			{