Enabled multiple inheritance, and removed its option, in the C# generator.

Signed-off-by: Dimitar Dobrev <dpldobrev@protonmail.com>

src/Generator/Driver.cs

@@ -322,7 +322,7 @@ namespace CppSharp
                 }
             }
 
-            if (Options.GenerateInterfacesForMultipleInheritance)
+            if (Options.IsCSharpGenerator)
             {
                 TranslationUnitPasses.AddPass(new MultipleInheritancePass());
                 TranslationUnitPasses.AddPass(new ParamTypeToInterfacePass());

src/Generator/Options.cs

@@ -91,7 +91,6 @@ namespace CppSharp
         public bool OutputInteropIncludes;
         public bool GenerateFunctionTemplates;
         public bool GeneratePartialClasses;
-        public bool GenerateInterfacesForMultipleInheritance;
         public bool GenerateInternalImports;
         public bool GenerateClassMarshals;
         public bool GenerateInlines;

tests/CSharp/CSharp.cs

@@ -150,7 +150,6 @@ namespace CppSharp.Tests
 
         public override void SetupPasses(Driver driver)
         {
-            driver.Options.GenerateInterfacesForMultipleInheritance = true;
             driver.Options.GeneratePropertiesAdvanced = true;
             // To ensure that calls to constructors in conversion operators
             // are not ambiguous with multiple inheritance pass enabled.