Cherrypick for csharp, including:

Add preserve UnknownFields
Compare floating point values bitwise
Add auto-generated header to C# generated files

1 files changed, 3 insertions, 2 deletions

diff --git a/csharp/src/Google.Protobuf/Collections/RepeatedField.cs b/csharp/src/Google.Protobuf/Collections/RepeatedField.cs
index 6063ff61..c18b63e2 100755
--- a/csharp/src/Google.Protobuf/Collections/RepeatedField.cs
+++ b/csharp/src/Google.Protobuf/Collections/RepeatedField.cs
@@ -51,6 +51,7 @@ namespace Google.Protobuf.Collections
         , IReadOnlyList<T>
 #endif
     {
+        private static readonly EqualityComparer<T> EqualityComparer = ProtobufEqualityComparers.GetEqualityComparer<T>();
         private static readonly T[] EmptyArray = new T[0];
         private const int MinArraySize = 8;
 
@@ -434,7 +435,7 @@ namespace Google.Protobuf.Collections
             {
                 return false;
             }
-            EqualityComparer<T> comparer = EqualityComparer<T>.Default;
+            EqualityComparer<T> comparer = EqualityComparer;
             for (int i = 0; i < count; i++)
             {
                 if (!comparer.Equals(array[i], other.array[i]))
@@ -454,7 +455,7 @@ namespace Google.Protobuf.Collections
         public int IndexOf(T item)
         {
             ProtoPreconditions.CheckNotNullUnconstrained(item, nameof(item));
-            EqualityComparer<T> comparer = EqualityComparer<T>.Default;
+            EqualityComparer<T> comparer = EqualityComparer;
             for (int i = 0; i < count; i++)
             {
                 if (comparer.Equals(array[i], item))