Added new FindPass method to get the pass of a certain type.

src/Generator/Passes/PassBuilder.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Linq;
 using CppSharp.Passes;
 
 namespace CppSharp
@@ -32,5 +33,13 @@ namespace CppSharp
                 pass.VisitLibrary(Driver.Library);
             }
         }
+
+        /// <summary>
+        /// Finds a previously-added pass of the given type.
+        /// </summary>
+        public T FindPass<T>() where T : TranslationUnitPass
+        {
+            return Passes.OfType<T>().Select(pass => pass as T).FirstOrDefault();
+        }
     }
 }