C#: Mark event accessors without bodies as compiler generated

Author: hvitved

csharp/extractor/Semmle.Extraction.CSharp/Entities/EventAccessor.cs

@@ -52,6 +52,11 @@ public override void Populate(TextWriter trapFile)
                 trapFile.event_accessor_location(this, l);
 
             Overrides(trapFile);
+
+            if (Symbol.FromSource() && Block is null)
+            {
+                trapFile.compiler_generated(this);
+            }
         }
 
         public static EventAccessor Create(Context cx, IMethodSymbol symbol, IEventSymbol @event) =>