Add the method to the marshaling context when handling value type ctors.

This fixes a marshaling regression with extra erroneous "&" which was caused by the fix done a couple days ago.

src/Generator/Generators/CLI/CLISourcesTemplate.cs

@@ -640,6 +640,7 @@ namespace CppSharp.Generators.CLI
             {
                 var ctx = new MarshalContext(Driver)
                               {
+                                  Function = method,
                                   Parameter = param,
                                   ArgName = param.Name,
                                   ParameterIndex = paramIndex++